Mette Kalager

• Botteri, Edoardo; Holme, Øyvind; Løberg, Magnus; Bretthauer, Michael; Kalager, Mette & Randel, Kristin Ranheim [Show all 7 contributors for this article] (2026). Twenty-Three–Year Benefits of Sigmoidoscopy Screening for Colorectal Cancer A Randomized Trial. Annals of Internal Medicine. ISSN 0003-4819. 179(6), p. 804–811. doi: 10.7326/annals-25-05456. Full text in Research Archive Show summary

  Background: Meta-analyses of randomized trials have shown that sigmoidoscopy screening reduces colorectal cancer (CRC) incidence and death for 15 years. Objective: To report the benefits of sigmoidoscopy after 23 years. Design: Randomized controlled trial. (NORCCAP [Norwegian Colorectal Cancer Prevention], ClinicalTrials.gov: NCT00119912) Setting: Population of Oslo and Telemark County, Norway. Participants: Persons aged 50 to 64 years without CRC at randomization. Intervention: Screening with once-only sigmoidoscopy, with or without 1 fecal immunochemical test, or no screening. Measurements: Colorectal cancer incidence and death. Results: A total of 100 210 persons were randomly assigned, and 98 654 were included in intention-to-screen analyses: 20 552 in the screening group and 78 102 in the no-screening group. Participation with screening was 61.4% in men and 64.7% in women. In men, the 23-year cumulative risk for CRC was 4.3% in the screening group and 6.0% in the no-screening group, corresponding to a risk difference of −1.7 percentage points (95% CI, −2.2 to −1.2 percentage points). In women, the corresponding risks were 4.2% and 4.7%, yielding a risk difference of −0.5 percentage points (CI, −1.0 to −0.01 percentage points). In men, the 23-year cumulative risk for CRC death was 1.4% in the screening group and 2.2% in the no-screening group, corresponding to a risk difference of −0.8 percentage points (CI, −1.1 to −0.5 percentage points). In women, the corresponding risks were 1.3% and 1.4%, yielding a risk difference of −0.1 percentage points (CI, −0.3 to 0.1 percentage points). The effect was strongest for rectosigmoid cancer. The addition of fecal blood testing to sigmoidoscopy did not change screening benefits. Limitation: Follow-up through national registries. Conclusion: Offering sigmoidoscopy screening in Norway reduced CRC incidence more in men than in women and reduced CRC death only in men.

• Kaminski, Michal F; Kalager, Mette; Løberg, Magnus; Emilsson, Louise; Macios, Anna & Samy, Faye [Show all 22 contributors for this article] (2026). Long-term effects of colonoscopy screening on colorectal cancer incidence and mortality: a multicountry, population-based randomised controlled trial. The Lancet. ISSN 0140-6736. doi: 10.1016/s0140-6736(26)00508-8. Full text in Research Archive Show summary

  Background We previously reported the 10-year effects of colonoscopy screening on colorectal cancer incidence and mortality. Here, we report the effects after 13 years of follow-up. Methods In this multicountry, population-based randomised controlled trial, 84 583 men and women aged 55–64 years at enrolment from Norway, Poland, and Sweden were randomly allocated (1:2) to colonoscopy screening or no screening and analysed. The primary outcomes were colorectal cancer incidence and mortality after 10–15 years of follow-up in intention-to-screen analyses, with first analysis after 10 years, and repeated every other year or at longer intervals. This trial is registered with ClinicalTrials.gov, NCT00883792, and is ongoing. Findings At 13 years of follow-up, colorectal cancer incidence was 375 colorectal cancers (1·46%) of 28 217 individuals in the screening group and 912 colorectal cancers (1·80%) of 56 366 individuals in the no-screening group. The risk ratio (RR) was 0·81 (95% CI 0·71–0·90) in intention-to-screen analyses and 0·55 (0·33–0·81) in per-protocol analyses. The risk for proximal colorectal cancer was 129 (0·51%) in the screening group versus 283 (0·56%) in the no-screening group (RR 0·91 [0·71–1·09]), and the risk for distal colorectal cancer was 224 (0·87%) in the screening group versus 563 (1·11%) in the no-screening group (RR 0·79 [0·65–0·89]; interaction p<0·0001). In men, the colorectal cancer risk was 214 (1·69%) of 14 154 in the screening group and 541 (2·19%) of 28 247 in the no-screening group (RR 0·77 [0·64 to –0·88]); in women, the risk was 161 (1·24%) of 14 063 in the screening group versus 371 (1·43%) of 28 119 in the no-screening group (RR 0·87 [0·70 to 1·02]; interaction p<0·0001). Colorectal cancer mortality was 106 (0·41%) of 28 217 in the screening group and 236 (0·47%) of 56 366 in the no-screening group (intention-to-screen RR 0·88 [0·68–1·08], per-protocol RR 0·70 [0·26–1·25]). The observed colorectal cancer mortality in the non-screening group (0·47%) was substantially lower than expected at the time of designing the trial (0·82%). Interpretation One colonoscopy significantly reduced colorectal cancer incidence but not mortality over 13 years. Colorectal cancer mortality was lower in both study groups than when the trial was designed.

• Zaalberg, Irene C.; Ketelaars, Steven L.C.; Jodal, Henriette C.; Løberg, Magnus; Kalager, Mette & Meijer, Gerrit A. [Show all 8 contributors for this article] (2026). Aneuploidy patterns in colorectal cancer. Cell reports. 45(1), p. 116721–116721. doi: 10.1016/j.celrep.2025.116721. Full text in Research Archive
• Mori, Yuichi; Wang, Pu; Kamba, Shunsuke; Liu, Lin; Siersema, Peter D. & Hassan, Cesare [Show all 24 contributors for this article] (2025). Addressing Colonoscopy Burden Due to Artificial Intelligence Devices for Polyp Detection. Gastroenterology. ISSN 0016-5085. 170(2), p. 398–400. doi: 10.1053/j.gastro.2025.08.019. Full text in Research Archive
• Halvorsen, Natalie Grace Mosteiro; Hassan, Cesare; Correale, Loredana; Pilonis, Nastazja Dagny; Helsingen, Lise Mørkved & Spadaccini, Marco [Show all 14 contributors for this article] (2025). Benefits, burden, and harms of computer aided polyp detection with artificial intelligence in colorectal cancer screening: microsimulation modelling study. BMJ Medicine. 4(1). doi: 10.1136/bmjmed-2025-001446. Full text in Research Archive
• Högdén, Amanda; Perrin, Vera; Adami, Hans Olov; Kalager, Mette; Jess, Tine & Ye, Weimin [Show all 10 contributors for this article] (2025). Temporal trends in surgical treatment of inflammatory bowel disease following introduction of biological drugs in Norway and Sweden. BMJ open gastroenterology. 12(1). doi: 10.1136/bmjgast-2025-001828. Full text in Research Archive
• Olabintan, Olaolu; Halvorsen, Natalie Grace Mosteiro; Baddeley, Robin; Kudo, Shin Ei; Barua, Ishita & Misawa, Masashi [Show all 21 contributors for this article] (2025). Environmental impact of computer-aided diagnosis in colonoscopy: A carbon footprint assessment of a prospective study cohort. Endoscopy. ISSN 0013-726X. 58(03), p. 303–309. doi: 10.1055/a-2717-8365. Full text in Research Archive Show summary

  Background The environmental impact of computer-aided diagnosis (CADx) in colonoscopy is unknown. The potential to reduce greenhouse gas emissions by limiting unnecessary polypectomies may be offset by emissions associated with CADx devices. We quantified and compared the carbon footprint of colonoscopy with and without CADx. Methods Life-cycle carbon emissions associated with endoscopic snares, polyp traps, histopathology, and CADx devices were estimated using life-cycle assessment software. The effect of CADx was estimated by the carbon dioxide equivalent (CO2e) emissions related to outcomes from a prospective cohort of patients who underwent colonoscopy with optical diagnosis under a leave-in-situ strategy (i.e. rectosigmoid polyps ≤5 mm predicted as non-neoplastic were not removed) with and without CADx assistance. Results We analyzed 1134 individuals (median age 67 years, 59% male) with 1716 colorectal polyps. Colonoscopy with CADx reduced the number of snares and polyp traps from 567 to 543 (difference: 24) and histopathology submissions from 1343 to 1278 (difference: 65). However, the total carbon footprint increased from 832 kg CO2e (95%CI 815 to 847) without CADx to 946 kg CO2e (95%CI 927 to 965) with CADx, corresponding to an absolute increase of 114 kg CO2e (95%CI 80 to 150) or 0.10 kg CO2e per colonoscopy. Conclusion Using CADx under a leave-in-situ strategy increased the environmental burden of colonoscopy.

• Budzyń, Krzysztof; Romańczyk, Marcin; Kitala, Diana; Kołodziej, Paweł; Bugajski, Marek & Adami, Hans Olov [Show all 21 contributors for this article] (2025). Endoscopist deskilling risk after exposure to artificial intelligence in colonoscopy: a multicentre, observational study. The Lancet Gastroenterology and Hepatology. ISSN 2468-1253. 10(10), p. 896–903. doi: 10.1016/S2468-1253(25)00133-5. Full text in Research Archive
• Nilsen, Jens Aksel; Juul, Frederik Emil; Egeland, Anders; Tandberg, Petter; Norvard, Espen & Lund-Iversen, Terje [Show all 9 contributors for this article] (2025). Colorectal ESD in a nordic community hospital: learning curves and clinical outcomes. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. 60(11), p. 1043–1052. doi: 10.1080/00365521.2025.2553279. Full text in Research Archive
• Akwiwu, Eddymurphy U; Klausch, Thomas; Jodal, Henriette C.; Carvalho, Beatriz; Løberg, Magnus & Kalager, Mette [Show all 8 contributors for this article] (2025). Fitting a progressive 3-state colorectal cancer model to interval-censored surveillance data under outcome-dependent sampling using a weighted likelihood approach. American Journal of Epidemiology. ISSN 0002-9262. 194(6), p. 1764–1775. doi: 10.1093/aje/kwae307. Full text in Research Archive
• Young, Jessica C.; Helsingen, Lise Mørkved; Refsum, Erle; Högdén, Amanda; Perrin, Vera & Løberg, Magnus [Show all 20 contributors for this article] (2025). Temporal trends in characteristics and management of inflammatory bowel disease. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. 60(5), p. 421–429. doi: 10.1080/00365521.2025.2478166. Full text in Research Archive Show summary

  Background and aims: Inflammatory bowel disease (IBD) requires complex clinical management. Despite substantial advancements in endoscopy and in pharmacotherapies for patients with IBD, it remains unclear how these developments have influenced IBD incidence and clinical care. We aim to describe changes in diagnostic and therapeutic practices in IBD management. Methods: All individuals diagnosed with IBD between 1987 and 2016 were identified from nationwide registries in Norway and Sweden. We performed detailed chart abstractions for a random sample of the cohort. We describe patient characteristics, disease extent, endoscopic practices, pathology diagnostics, pharmacological therapy and surgical management, stratifying by Crohn’s disease (CD) and ulcerative colitis [UC], comparing patients diagnosed before (pre-biologic period, 1987–1999), and after the introduction of biologic drugs (biologic period, 2000–2016). Results: Chart abstraction was completed for 791 individuals (UC: 58.8%, Crohn’s disease: 40.2%, unclassified IBD: 1.0%). Comparing the biologic period to the pre-biologic period, we observed an increase in endoscopies after diagnosis, more frequent colonoscopies, and a decrease in colon resection rates. Among those diagnosed in 2007 or later compared with those diagnosed between 2000 and 2006, there was a higher treatment initiation rate of azathioprine, infliximab and adalimumab within 1 year after diagnosis. Conclusions: Our findings suggest a shift towards more frequent endoscopy, increased use of immunosuppressants and biologics, and decreased colon resection rates in recent periods.

• Halvorsen, Natalie Grace Mosteiro; Barua, Ishita; Kudo, Shin-Ei; Gulati, Shraddha; Misawa, Masashi & Mori, Kensaku [Show all 19 contributors for this article] (2025). Leaving colorectal polyps in situ with endocytoscopy assisted by computer-aided diagnosis: a cost-effectiveness study. Endoscopy. ISSN 0013-726X. 57, p. 611–619. doi: 10.1055/a-2532-9282. Full text in Research Archive
• Foroutan, Farid; Vandvik, Per Olav; Helsingen, Lise Mørkved; Kalager, Mette; Rutter, Matt & Selby, Kevin [Show all 26 contributors for this article] (2025). Computer aided detection and diagnosis of polyps in adult patients undergoing colonoscopy: a living clinical practice guideline. The BMJ. doi: 10.1136/bmj-2024-082656. Full text in Research Archive
• Pilonis, Nastazja Dagny; Spychalski, Piotr; Kalager, Mette; Løberg, Magnus; Wieszczy, Paulina & Didkowska, Joanna [Show all 12 contributors for this article] (2025). Adenoma Detection Rates by Physicians and Subsequent Colorectal Cancer Risk. Journal of the American Medical Association (JAMA). ISSN 0098-7484. 333(5), p. 400–407. doi: 10.1001/jama.2024.22975. Full text in Research Archive
• Shi, Joy; Løberg, Magnus; Kalager, Mette; Wieszczy, Paulina; Pilonis, Nastazja Dagny & Adami, Hans Olov [Show all 10 contributors for this article] (2025). Effect of colonoscopy screening on risks of colorectal cancer and related death: instrumental variable estimation of per-protocol effects. European Journal of Epidemiology (EJE). ISSN 0393-2990. doi: 10.1007/s10654-025-01209-w. Full text in Research Archive
• Juul, Frederik Emil; Bretthauer, Michael; Johnsen, Peter Holger; Samy, Faye; Tonby, Kristian & Berdal, Jan-Erik [Show all 29 contributors for this article] (2025). Fecal Microbiota Transplantation Versus Vancomycin for Primary Clostridioides difficile Infection : A Randomized Controlled Trial. Annals of Internal Medicine. ISSN 0003-4819. 178(7), p. 940–947. doi: 10.7326/ANNALS-24-03285. Full text in Research Archive
• Hassan, Cesare; Rizkala, Tommy; Mori, Yuichi; Spadaccini, Marco; Misawa, Masashi & Antonelli, Giulio [Show all 33 contributors for this article] (2024). Computer-aided diagnosis for the resect-and-discard strategy for colorectal polyps: a systematic review and meta-analysis. The Lancet Gastroenterology and Hepatology. ISSN 2468-1253. 9(11), p. 1010–1019. doi: 10.1016/S2468-1253(24)00222-X. Full text in Research Archive
• Nilsen, Jens Aksel; Bernklev, Linn; Bretthauer, Michael; Kalager, Mette; Jodal, Henriette C. & Løberg, Magnus [Show all 9 contributors for this article] (2024). Kirurgisk behandling av benigne kolorektale polypper 2008–21. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 144(10). doi: 10.4045/tidsskr.23.0722. Full text in Research Archive
• Kalager, Mette (2024). Om forhåndssamtaler, retningslinjer og randomisering. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 144(13). doi: 10.4045/tidsskr.24.0539. Full text in Research Archive
• Juul, Frederik Emil; Cross, Amanda J.; Schoen, Robert E.; Senore, Carlo; Pinsky, Paul F. & Miller, Eric A. [Show all 17 contributors for this article] (2024). Effectiveness of Colonoscopy Screening vs Sigmoidoscopy Screening in Colorectal Cancer. JAMA Network Open. 7(2). doi: 10.1001/jamanetworkopen.2024.0007. Full text in Research Archive Show summary

  Importance: Randomized clinical screening trials have shown that sigmoidoscopy screening reduces colorectal cancer (CRC) incidence and mortality. Colonoscopy has largely replaced sigmoidoscopy for CRC screening, but long-term results from randomized trials on colonoscopy screening are still lacking. Objective: To estimate the additional screening benefit of colonoscopy compared with sigmoidoscopy. Design, setting, and participants: This comparative effectiveness simulation study pooled data on 358 204 men and women randomly assigned to sigmoidoscopy screening or usual care in 4 randomized sigmoidoscopy screening trials conducted in Norway, Italy, the US, and UK with inclusion periods in the years 1993 to 2001. The primary analysis of the study was conducted from January 19 to December 30, 2021. Intervention: Invitation to endoscopic screening. Main outcomes and measures: Primary outcomes were CRC incidence and mortality. Using pooled 15-year follow-up data, colonoscopy screening effectiveness was estimate

• Bretthauer, Michael & Kalager, Mette (2023). What is my risk, doctor? How to convey disease risk and treatment effects. The BMJ. doi: 10.1136/bmj-2022-075289. Full text in Research Archive
• Langeland, Eline Aurvoll; Pisani, Synne E. R.; Kalager, Mette; Bretthauer, Michael & Helsingen, Lise Mørkved (2023). Følger Helsedirektoratets retningslinjer internasjonale standarder for troverdighet? Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 143(14). doi: 10.4045/tidsskr.23.0110. Full text in Research Archive Show summary

  BAKGRUNN - Helsedirektoratet produserer nasjonale faglige retningslinjer for helsetjenesten, og utviklingen av retningslinjene skal følge internasjonale standarder for troverdighet. Vi undersøkte om standardene blir fulgt.<p> <p>MATERIALE OG METODE - Vi benyttet skåringsverktøyet National Guideline Clearinghouse Extent of Adherence to Trustworthy Standards Instrument (NEATS), og vurderte ett tilfeldig valgt kapittel fra nasjonale faglige retningslinjer publisert eller oppdatert fra 2013 til januar 2022. NEATS har 15 domener: tre vurderes med svaralternativene ja/nei/ukjent, og tolv vurderes på en Likert-skala fra 1 til 5, der 1 tilsvarer svært lav troverdighet og 5 utmerket troverdighet. Vurderingene ble gjort individuelt av to forfattere. Interobservatørsamsvar ble vurdert med eksakt og nært samsvar samt Cohens kappa.<p> <p>RESULTATER - Vi inkluderte 60 gjeldende retningslinjer. For ni av tolv NEATS-domener vurdert med Likert-skala var det svært lav eller lav overholdelse av standarder for troverdige retningslinjer (median skår 1 eller 2). Domenene med lavest skår (median skår 1) var «studieseleksjon», «beskrivelse av studiene og resultatene», «gradering av styrken på anbefalingene» og «ekstern høring». Domenet med høyest skår var «spesifikk og utvetydig formulering av anbefalingene» (median skår 4).<p> <p>FORTOLKNING - Flertallet av de nasjonale faglige retningslinjene overholdt i liten grad standarder for troverdige retningslinjer vurdert med skåringsverktøyet NEATS.<p>

• Tønnesen, Christer Julseth; Hjelmesæth, Jøran Sture; Aabakken, Lars; Lund, Randi Størdal; Johnson, Line Kristin & Hertel, Jens Kristoffer [Show all 9 contributors for this article] (2023). A pilot study of implementation of endoscopic sleeve gastroplasty (ESG) in Norway. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. 58(10), p. 1180–1184. doi: 10.1080/00365521.2023.2204389. Full text in Research Archive Show summary

  Bariatric surgery is the most effective treatment for obesity but is invasive and associated with serious complications. Endoscopic sleeve gastroplasty (ESG) is a less invasive weight loss procedure to reduce the stomach volume by full-thickness sutures. ESG has been adopted in many countries, but implementation at Scandinavian centres has not yet been documented. We performed a clinical pilot trial at a Norwegian centre with the primary objective to assess the feasibility of the ESG procedure. Patients and methods We included the first 10 patients treated with ESG at a Norwegian centre in a single-arm pilot study. The eligibility criteria were either a body mass index (BMI) of 40–49.9 kg/m2, BMI 35–39.9 kg/m2 and at least one obesity-related comorbidity, or BMI 30–34.9 kg/m2 and type 2 diabetes. Patient follow-up resembled the scheme used for bariatric surgery at the center, including dietary plans and outpatient visits. Results All procedures were technically successful except for one patient who had adhesions between the stomach and anterior abdominal wall, related to a prior hernia repair, resulting in less-than-intended stomach volume reduction. Mean total body weight loss (TBWL) after 26 and 52 weeks was 12.2% (95% CI 8.1–16.2) and 9.1% (95% CI 3.3 − 15.0). One patient experienced a minor suture-induced diaphragmatic injury, which was successfully managed conservatively. Conclusions This first Scandinavian clinical trial of ESG, documenting the implementation of the procedure at a Norwegian center, demonstrated acceptable feasibility and safety, with large variations in individual weight loss during the 52-week follow-up period.

• Skaare, Dagfinn; Hannisdal, Anja; Kalager, Mette & Berild, Dag (2023). Måling av bruk av bredspektrede antibiotika i sykehus med etablerte og nye indikatorer. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 143(6). doi: 10.4045/tidsskr.22.0427. Full text in Research Archive Show summary

  Målet om 30 % reduksjon i bruk av bredspektrede antibiotika i sykehus fra 2012 til 2020 ble ikke nådd målt med standardindikatoren definerte døgndoser (DDD) per 100 liggedøgn. Vi ønsket å undersøke påliteligheten av standardindikatoren og utvalgte alternative indikatorer for antibiotikabruk, og hva som var reell reduksjon i bruk. MATERIALE OG METODE Vi inkluderte ti DDD-baserte indikatorer med justering for kombinasjoner av aktivitetsmarkør, innleggelseskategori (døgnopphold vs. alle innleggelser) og pasientsammensetning, og evaluerte disse etter hvordan hver indikator korrelerte med antibiotikaresistens i en egenutviklet modell. Deretter beregnet vi bruk av bredspektrede antibiotika i sykehus for perioden 2012–20 med indikatorer vurdert som valide, og sammenlignet indikatorene mht. endring i bruk og rangering av sykehus etter bruk. Som aktivitetsnøytral referanseindikator (nasjonalt og regionalt) benyttet vi forbruksrate (DDD per 1 000 innbyggere per døgn). RESULTATER Alle indikatorene for antibiotikabruk viste sterk korrelasjon med resistens. For fem indikatorer var korrelasjonen statistisk signifikant, hvorav indikatoren som kombinerte justering for totalt antall innlagte pasienter og pasientsammensetning, ga best samsvar med forbruksrate (35,6 %). Samme indikator viste også størst reduksjon i bruk (29,3 %) og ga flest sykehus som oppnådde minst 30 % reduksjon (13 av 22). FORTOLKNING Kombinert justering for antall innlagte pasienter og pasientsammensetning er en ny, robust indikator for antibiotikabruk som er egnet for sykehus på alle nivåer. Indikatoren kan benyttes parallelt med forbruksrate, som bør vurderes som ny standardindikator på nasjonalt og regionalt nivå.

• Jodal, Henriette C.; Akwiwu, Eddymurphy U.; Lemmens, Margriet; Diemen, Pien M Delis-van; Klotz, Dagmar & Leon, Leticia G [Show all 17 contributors for this article] (2023). Risk Prediction of Metachronous Colorectal Cancer from Molecular Features of Adenomas: A Nested Case-Control Study. Cancer Research Communications. 3(11), p. 2292–2301. doi: 10.1158/2767-9764.CRC-23-0186. Full text in Research Archive
• Bretthauer, Michael; Wieszczy, Paulina; Løberg, Magnus; Kamiński, Michał Filip; Werner, Tarjei Fiskergård & Helsingen, Lise Mørkved [Show all 10 contributors for this article] (2023). Estimated Lifetime Gained with Cancer Screening Tests: A Meta-Analysis of Randomized Clinical Trials. JAMA Internal Medicine. ISSN 2168-6106. 183(11), p. 1196–1203. doi: 10.1001/jamainternmed.2023.3798. Full text in Research Archive
• Yu, Jingru; Refsum, Erle; Wieszczy, Paulina; Helsingen, Lise Mørkved; Perrin, Vera & Högdén, Amanda [Show all 12 contributors for this article] (2023). Risk of malignant lymphomas in patients with inflammatory bowel disease: a population-based cohort study. BMJ open gastroenterology. 10(1). doi: 10.1136/bmjgast-2022-001037. Full text in Research Archive
• Jodal, Henriette C.; Wieszczy, Paulina; Klotz, Dagmar; Herfindal, Magnhild; Barua, Ishita & Tag, Petter [Show all 13 contributors for this article] (2023). A Comparison of Risk Classification Systems of Colorectal Adenomas: A Case-Cohort Study. Gastroenterology. ISSN 0016-5085. 165, p. 483–491. doi: 10.1053/j.gastro.2023.04.028. Full text in Research Archive Show summary

  Background & Aims Because post-polypectomy surveillance uses a growing proportion of colonoscopy capacity, more targeted surveillance is warranted. We therefore compared surveillance burden and cancer detection using 3 different adenoma classification systems. Methods In a case-cohort study among individuals who had adenomas removed between 1993 and 2007, we included 675 individuals with colorectal cancer (cases) diagnosed a median of 5.6 years after adenoma removal and 906 randomly selected individuals (subcohort). We compared colorectal cancer incidence among high- and low-risk individuals defined according to the traditional (high-risk: diameter ≥10 mm, high-grade dysplasia, villous growth pattern, or 3 or more adenomas), European Society of Gastrointestinal Endoscopy (ESGE) 2020 (high-risk: diameter ≥10 mm, high-grade dysplasia, or 5 or more adenomas), and novel (high-risk: diameter ≥20 mm or high-grade dysplasia) classification systems. For the different classification systems, we calculated the number of individuals recommended frequent surveillance colonoscopy and estimated number of delayed cancer diagnoses. Results Four hundred and thirty individuals with adenomas (52.7%) were high risk based on the traditional classification, 369 (45.2%) were high risk based on the ESGE 2020 classification, and 220 (27.0%) were high risk based on the novel classification. Using the traditional, ESGE 2020, and novel classifications, the colorectal cancer incidences per 100,000 person-years were 479, 552, and 690 among high-risk individuals, and 123, 124, and 179 among low-risk individuals, respectively. Compared with the traditional classification, the number of individuals who needed frequent surveillance was reduced by 13.9% and 44.2%, respectively, and 1 (3.4%) and 7 (24.1%) cancer diagnoses were delayed using the ESGE 2020 and novel classifications. Conclusions Using the ESGE 2020 and novel risk classifications will substantially reduce resources needed for colonoscopy surveillance after adenoma removal.

• Holme, Øyvind; Kalager, Mette; Bretthauer, Michael; Adami, Hans Olov; Helsingen, Lise Mørkved & Løberg, Magnus (2023). Ongoing Trials Will Not Determine the Comparative Effectiveness of Colorectal Cancer Screening Tests. Gastroenterology. ISSN 0016-5085. 164(6), p. 856–860. doi: 10.1053/j.gastro.2020.02.071. Full text in Research Archive
• Juul, Frederik Emil; Garborg, Kjetil Kjeldstad; Nesbakken, Philip Eugen; Løberg, Magnus; Wieszczy, Paulina & Cubiella, Joaquín [Show all 19 contributors for this article] (2022). Rates of repeated colonoscopies to clean the colon from low-risk and high-risk adenomas: Results from the EPoS trials. Gut. ISSN 0017-5749. doi: 10.1136/gutjnl-2022-327696. Full text in Research Archive Show summary

  Objective High-quality colonoscopy (adequate bowel preparation, whole-colon visualisation and removal of all neoplastic polyps) is a prerequisite to start polyp surveillance, and is ideally achieved in one colonoscopy. In a large multinational polyp surveillance trial, we aimed to investigate clinical practice variation in number of colonoscopies needed to enrol patients with low-risk and high-risk adenomas in polyp surveillance. Design We retrieved data of all patients with low-risk adenomas (one or two tubular adenomas <10 mm with low-grade dysplasia) and high-risk adenomas (3–10 adenomas, ≥1 adenoma ≥10 mm, high-grade dysplasia or villous components) in the European Polyp Surveillance trials fulfilling certain logistic and methodologic criteria. We analysed variations in number of colonoscopies needed to achieve high-quality colonoscopy and enter polyp surveillance by endoscopy centre, and by endoscopists who enrolled ≥30 patients. Results The study comprised 15 581 patients from 38 endoscopy centres in five European countries; 6794 patients had low-risk and 8787 had high-risk adenomas. 961 patients (6.2%, 95% CI 5.8% to 6.6%) underwent two or more colonoscopies before surveillance began; 101 (1.5%, 95% CI 1.2% to 1.8%) in the low-risk group and 860 (9.8%, 95% CI 9.2% to 10.4%) in the high-risk group. Main reasons were poor bowel preparation (21.3%) or incomplete colonoscopy/polypectomy (14.4%) or planned second procedure (27.8%). Need of repeat colonoscopy varied between study centres ranging from 0% to 11.8% in low-risk adenoma patients and from 0% to 63.9% in high-risk adenoma patients. On the second colonoscopy, the two most common reasons for a repeat (third) colonoscopy were piecemeal resection (26.5%) and unspecified reason (23.9%). Conclusion There is considerable practice variation in the number of colonoscopies performed to achieve complete polyp removal, indicating need for targeted quality improvement to reduce patient burden. Trial registration number NCT02319928.

• Barua, Ishita; Misawa, Masashi; Brown, Jeremy R. Glissen; Walradt, Trent; Kudo, Shin-ei & Sheth, Sunil G. [Show all 19 contributors for this article] (2022). Speedometer for withdrawal time monitoring during colonoscopy: a clinical implementation trial. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. doi: 10.1080/00365521.2022.2154616. Full text in Research Archive
• Ribe, Sara Gunnestad; Botteri, Edoardo; Løberg, Magnus; Randel, Kristin Ranheim; Kalager, Mette & Nilsen, Jens Aksel [Show all 8 contributors for this article] (2022). Impact of time between faecal immunochemical tests in colorectal cancer screening on screening results: A natural experiment. International Journal of Cancer. ISSN 0020-7136. doi: 10.1002/ijc.34351. Full text in Research Archive
• Anda, Erik Eik; Braaten, Tonje Bjørndal; Borch, Kristin Benjaminsen; Nøst, Therese Haugdahl; Chen, Sairah Lai Fa & Lukic, Marko [Show all 14 contributors for this article] (2022). Seroprevalence of antibodies against SARS-CoV-2 in the adult population during the pre-vaccination period, Norway, winter 2020/21. Eurosurveillance. ISSN 1025-496X. 27(13), p. 1–10. doi: 10.2807/1560-7917.ES.2022.27.13.2100376. Full text in Research Archive Show summary

  Background: Since March 2020, 440 million people worldwide have been diagnosed with COVID-19, but the true number of infections with SARS-CoV-2 is higher. SARS-CoV-2 antibody seroprevalence can add crucial epidemiological information about population infection dynamics. Aim: To provide a large population-based SARS-CoV-2 seroprevalence survey from Norway; we estimated SARS-CoV-2 seroprevalence before introduction of vaccines and described its distribution across demographic groups. Methods: In this population-based cross-sectional study, a total of 110,000 people aged 16 years or older were randomly selected during November–December 2020 and invited to complete a questionnaire and provide a dried blood spot (DBS) sample. Results: The response rate was 30% (31,458/104,637); compliance rate for return of DBS samples was 88% (27,700/31,458). National weighted and adjusted seroprevalence was 0.9% (95% CI (confidence interval): 0.7–1.0). Seroprevalence was highest among those aged 16–19 years (1.9%; 95% CI: 0.9–2.9), those born outside the Nordic countries 1.4% (95% CI: 1.0–1.9), and in the counties of Oslo 1.7% (95% CI: 1.2–2.2) and Vestland 1.4% (95% CI: 0.9– 1.8). The ratio of SARS-CoV-2 seroprevalence (0.9%) to cumulative incidence of virologically detected cases by mid-December 2020 (0.8%) was slightly above one. SARS-CoV-2 seroprevalence was low before introduction of vaccines in Norway and was comparable to virologically detected cases, indicating that most cases in the first 10 months of the pandemic were detected. Conclusion: Findings suggest that preventive measures including contact tracing have been effective, people complied with physical distancing recommendations, and local efforts to contain outbreaks have been essential.

• Yu, Jingru; Refsum, Erle; Perrin, Vera; Helsingen, Lise Mørkved; Wieszczy, Paulina & Løberg, Magnus [Show all 11 contributors for this article] (2022). Inflammatory bowel disease and risk of adenocarcinoma and neuroendocrine tumors in the small bowel. Annals of Oncology. ISSN 0923-7534. p. 1–8. doi: 10.1016/j.annonc.2022.02.226. Full text in Research Archive
• Barua, Ishita; Wieszczy, Paulina; Kudo, Shin-ei; Masashi, Misawa; Holme, Øyvind & Gulati, Shraddha [Show all 34 contributors for this article] (2022). Real-Time Artificial Intelligence–Based Optical Diagnosis of Neoplastic Polyps during Colonoscopy. NEJM Evidence. 1(6). doi: 10.1056/EVIDoa2200003. Full text in Research Archive
• Ainechi, Diba; Misawa, Masashi; Barua, Ishita; Larsen, Solveig; Paulsen, Vemund & Garborg, Kjetil Kjeldstad [Show all 21 contributors for this article] (2022). Impact of artificial intelligence on colorectal polyp detection for early-career endoscopists: an international comparative study. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. doi: 10.1080/00365521.2022.2070436. Full text in Research Archive Show summary

  Background Artificial intelligence (AI) for polyp detection is being introduced to colonoscopy, but there is uncertainty how this affects endoscopists’ ability to detect polyps and neoplasms. We performed a video-based study to address whether AI improved the endoscopists’ performance to detect polyps. Methods We established a dataset of 200 colonoscopy videos (length 5 s; 100 without polyps and 100 with one polyp). About 33 early-career endoscopists (50–400 colonoscopies performed) from 10 European countries classified each video as either ‘polyp present’ or ‘polyp not present’. The video assessment was performed twice with a four-week interval. The first assessment was performed without any AI tool, whereas the second was performed with an AI tool for polyp detection. The primary endpoint was early-career endoscopists’ sensitivity to detect polyps. Gold standard for presence and histology of polyps were confirmed by two expert endoscopists and pathologists, respectively. McNemar’s test was used for statistical significance. Results There were 86 neoplastic and 14 non-neoplastic polyps (mean size 5.6 mm) in the 100 videos with polyps. Early-career endoscopists’ sensitivity to detect polyps increased from 86.3% (95% confidence interval [CI]: 85.1–87.5%) to 91.7% (95%CI: 90.7–92.6%) with the AI aid (p < .0001). Their sensitivity to detect neoplastic polyps increased from 85.4% (95% CI: 84.0–86.7%) to 92.1% (95%CI: 91.1–93.1%) with the AI aid (p < .0001). Conclusion The polyp detection AI tool helped early-career endoscopists to increase their sensitivity to identify all polyps and neoplastic polyps during colonoscopy.

• Juul, Frederik Emil; Cross, Amanda J.; Schoen, Robert E.; Senore, Carlo; Pinsky, Paul & Miller, Eric [Show all 17 contributors for this article] (2022). 15-Year Benefits of Sigmoidoscopy Screening on Colorectal Cancer Incidence and Mortality : A Pooled Analysis of Randomized Trials. Annals of Internal Medicine. ISSN 0003-4819. 175(11), p. 1525–1533. doi: 10.7326/M22-0835. Full text in Research Archive Show summary

  Background: The effectiveness of screening for colorectal cancer (CRC) by sex and age in randomized trials is uncertain. Objective: To evaluate the 15-year effect of sigmoidoscopy screening on CRC incidence and mortality. Design: Pooled analysis of 4 large-scale randomized trials of sigmoidoscopy screening. Setting: Norway, the United States, the United Kingdom, and Italy. Participants: Women and men aged 55 to 64 years at enrollment. Intervention: Sigmoidoscopy screening. Measurements: Primary end points were cumulative incidence rate ratio (IRR) and mortality rate ratio (MRR) and rate differences after 15 years of follow-up comparing screening versus usual care in intention-to-treat analyses. Stratified analyses were done by sex, cancer site, and age at screening. Results: Analyses comprised 274 952 persons (50.7% women), 137 493 in the screening and 137 459 in the usual care group. Screening attendance was 58% to 84%. After 15 years, the rate difference for CRC incidence was 0.51 cases (95% CI, 0.40 to 0.63 cases) per 100 persons and the IRR was 0.79 (CI, 0.75 to 0.83). The rate difference for CRC mortality was 0.13 deaths (CI, 0.07 to 0.19 deaths) per 100 persons, and the MRR was 0.80 (CI, 0.72 to 0.88). Women had less benefit from screening than men for CRC incidence (IRR for women, 0.84 [CI, 0.77 to 0.91]; IRR for men, 0.75 [CI, 0.70 to 0.81]; P = 0.032 for difference) and mortality (MRR for women, 0.91 [CI, 0.77 to 1.17]; MRR for men, 0.73 [CI, 0.64 to 0.83]; P = 0.025 for difference). There was no statistically significant difference in screening effect between persons aged 55 to 59 years and those aged 60 to 64 years. Limitation: Data from the U.K. trial were less granular because of privacy regulations. Conclusion: This pooled analysis of all large randomized trials of sigmoidoscopy screening demonstrates a significant and sustained effect of sigmoidoscopy on CRC incidence and mortality for 15 years.

• Yu, Jingru; Refsum, Erle; Helsingen, Lise Mørkved; Folseraas, Trine; Ploner, Alexander & Wieszczy, Paulina [Show all 15 contributors for this article] (2022). Risk of hepato-pancreato-biliary cancer is increased by primary sclerosing cholangitis in patients with inflammatory bowel disease: A population-based cohort study. United European Gastroenterology Journal (UEG Journal). ISSN 2050-6406. 10(2), p. 212–224. doi: 10.1002/ueg2.12204. Full text in Research Archive Show summary

  Background There is continued uncertainty regarding the risks of hepato-pancreato-biliary cancers in patients with inflammatory bowel disease (IBD) with or without concomitant primary sclerosing cholangitis (PSC). Objective To give updated estimates on risk of hepato-pancreato-biliary cancers in patients with IBD, including pancreatic cancer, hepatocellular carcinoma, gall bladder cancer, and intra – and extrahepatic cholangiocarcinoma. Methods In a population-based cohort study, we included all patients diagnosed with IBD in Norway and Sweden from 1987 to 2016. The cohort comprised of 141,960 patients, identified through hospital databases and the National Patient Register. Participants were followed through linkage to national cancer, cause of death, and population registries. We calculated absolute risk and standardized incidence ratios (SIRs) of hepato-pancreato-biliary cancers by PSC and other clinical characteristics. Results Of the 141,960 IBD patients, 3.2% were diagnosed with PSC. During a median follow-up of 10.0 years, we identified 443 biliary tract cancers (SIR 5.2, 95% confidence interval [CI] 4.8–5.7), 161 hepatocellular carcinomas (SIR 2.4, 95% CI 2.0–2.7) and 282 pancreatic cancers (SIR 1.3, 95% CI 1.2–1.5). The relative risks were considerably higher in PSC-IBD patients, with SIR of 140 (95% CI 123–159) for biliary tract, 38.6 (95% CI 29.2–50.0) for hepatocellular, and 9.0 (95% CI 6.3–12.6) for pancreatic cancer. The SIRs were still slightly increased in non-PSC-IBD patients, compared to the general population. For biliary tract cancer, the cumulative probability at 25 years was 15.6% in PSC-IBD patients, and 0.4% in non-PSC-IBD patients. Conclusions The dramatically increased risks of hepato-pancreato-biliary cancers in PSC-IBD patients support periodic surveillance for these malignancies. While much lower, the excess relative risks in non-PSC-IBD patients were not trivial compared to non-IBD related risk factors.

• Mori, Yuichi; Wang, Pu; Løberg, Magnus; Misawa, Masashi; Repici, Alessandro & Spadaccini, Marco [Show all 26 contributors for this article] (2022). Impact of Artificial Intelligence on Colonoscopy Surveillance After Polyp Removal: A Pooled Analysis of Randomized Trials. Clinical Gastroenterology and Hepatology. ISSN 1542-3565. doi: 10.1016/j.cgh.2022.08.022. Full text in Research Archive Show summary

  Background and Aims Artificial intelligence (AI) tools aimed at improving polyp detection have been shown to increase the adenoma detection rate during colonoscopy. However, it is unknown how increased polyp detection rates by AI affect the burden of patient surveillance after polyp removal. Methods We conducted a pooled analysis of 9 randomized controlled trials (5 in China, 2 in Italy, 1 in Japan, and 1 in the United States) comparing colonoscopy with or without AI detection aids. The primary outcome was the proportion of patients recommended to undergo intensive surveillance (ie, 3-year interval). We analyzed intervals for AI and non-AI colonoscopies for the U.S. and European recommendations separately. We estimated proportions by calculating relative risks using the Mantel-Haenszel method. Results A total of 5796 patients (51% male, mean 53 years of age) were included; 2894 underwent AI-assisted colonoscopy and 2902 non-AI colonoscopy. When following U.S. guidelines, the proportion of patients recommended intensive surveillance increased from 8.4% (95% CI, 7.4%–9.5%) in the non-AI group to 11.3% (95% CI, 10.2%–12.6%) in the AI group (absolute difference, 2.9% [95% CI, 1.4%–4.4%]; risk ratio, 1.35 [95% CI, 1.16–1.57]). When following European guidelines, it increased from 6.1% (95% CI, 5.3%–7.0%) to 7.4% (95% CI, 6.5%–8.4%) (absolute difference, 1.3% [95% CI, 0.01%–2.6%]; risk ratio, 1.22 [95% CI, 1.01–1.47]). Conclusions The use of AI during colonoscopy increased the proportion of patients requiring intensive colonoscopy surveillance by approximately 35% in the United States and 20% in Europe (absolute increases of 2.9% and 1.3%, respectively). While this may contribute to improved cancer prevention, it significantly adds patient burden and healthcare costs.

• Akwiwu, Eddymurphy U.; Klausch, Thomas; Jodal, Henriette C.; Carvalho, Beatriz; Løberg, Magnus & Kalager, Mette [Show all 8 contributors for this article] (2022). A progressive three-state model to estimate time to cancer: a likelihood-based approach. BMC Medical Research Methodology. 22(1). doi: 10.1186/s12874-022-01645-2. Full text in Research Archive Show summary

  Background To optimize colorectal cancer (CRC) screening and surveillance, information regarding the time-dependent risk of advanced adenomas (AA) to develop into CRC is crucial. However, since AA are removed after diagnosis, the time from AA to CRC cannot be observed in an ethically acceptable manner. We propose a statistical method to indirectly infer this time in a progressive three-state disease model using surveillance data. Methods Sixteen models were specified, with and without covariates. Parameters of the parametric time-to-event distributions from the adenoma-free state (AF) to AA and from AA to CRC were estimated simultaneously, by maximizing the likelihood function. Model performance was assessed via simulation. The methodology was applied to a random sample of 878 individuals from a Norwegian adenoma cohort. Results Estimates of the parameters of the time distributions are consistent and the 95% confidence intervals (CIs) have good coverage. For the Norwegian sample (AF: 78%, AA: 20%, CRC: 2%), a Weibull model for both transition times was selected as the final model based on information criteria. The mean time among those who have made the transition to CRC since AA onset within 50 years was estimated to be 4.80 years (95% CI: 0; 7.61). The 5-year and 10-year cumulative incidence of CRC from AA was 13.8% (95% CI: 7.8%;23.8%) and 15.4% (95% CI: 8.2%;34.0%), respectively. Conclusions The time-dependent risk from AA to CRC is crucial to explain differences in the outcomes of microsimulation models used for the optimization of CRC prevention. Our method allows for improving models by the inclusion of data-driven time distributions.

• Jodal, Henriette C.; Juul, Frederik Emil; Barua, Ishita; Bretthauer, Michael; Kalager, Mette & Løberg, Magnus [Show all 7 contributors for this article] (2022). Emergency hospital admissions, prognosis, and population mortality in Norway during the first wave of the Covid-19 epidemic. Scandinavian Journal of Public Health. ISSN 1403-4948. 50(6), p. 795–802. doi: 10.1177/14034948221082959. Full text in Research Archive Show summary

  Background: During the first wave of the Covid-19 epidemic, a national lockdown was established in Norway, and inhabitants were asked to contact healthcare only if absolutely necessary. We investigated hospital admissions and mortality due to non-Covid-19 disease during the lockdown compared to previous years. Methods: We compared the number of emergency admissions and in-hospital fatality for diagnoses probably unaffected (acute myocardial infarction, acute abdominal conditions, cerebrovascular diseases) and affected by the lockdown (infections, injuries) in the South-Eastern Health Region of Norway during weeks 12–22, 2020, compared to the mean of the same period in the years 2017–2019. We also compared population mortality March–May 2020, to the mean of the same period in years 2017–2019. Results: A total of 280,043 emergency admissions were observed; 20,911 admissions probably unaffected, and 30,905 admissions probably affected by the lockdown. Admissions due to diagnoses probably unaffected was reduced by 12% (95% confidence interval (CI) 9–15%), compared to 2017–2019. Admissions for diagnoses probably affected was reduced by 30% (95% CI 28–32%). There was a 34% reduction in in-hospital fatality due to acute myocardial infarction (95% CI 4–56%), 19% due to infections (95% CI 1–33%), and no change for the other diagnoses, compared to 2017–2019. The risk of in-hospital mortality to total mortality was lower for acute myocardial infarction (relative risk 0.85, 95% CI 0.73–0.99) and injuries (relative risk 0.83, 95% CI 0.70–0.98). Conclusions: Even though fewer patients were admitted to hospital, there was no increase in in-hospital fatality or population mortality, indicating that those who were most in need still received adequate care.

• Pedersen, Ina Borgenheim; Rawa-Goleblewska, Anna; Calderwood, Audrey H.; Brix, Lone D.; Grode, Louise B. & Botteri, Edoardo [Show all 17 contributors for this article] (2022). Complete Polyp Resection with Cold versus Hot snare Polypectomy for Polyps sized 4-9 mm: A randomized controlled trial. Endoscopy. ISSN 0013-726X. 54(10), p. 961–969. doi: 10.1055/a-1734-7952. Full text in Research Archive Show summary

  Background: Endoscopic screening with polypectomy reduces the incidence of colorectal cancer (CRC). Incomplete polyp removal may attenuate the effect of screening. This randomized trial compared cold snare polypectomy (CSP) with hot snare polypectomy (HSP) in terms of complete polyp resection. Methods: We included patients ≥ 40 years of age at eight hospitals in four countries who had at least one non-pedunculated polyp of 4-9 mm detected at colonoscopy. Patients were randomized 1:1 to CSP or HSP. Biopsies from the resection margins were obtained systematically after polypectomy in both groups. We hypothesized that CSP would be non-inferior to HSP, with a non-inferiority margin of 5 %. Logistic regression models were fitted to identify the factors explaining incomplete resection. Results: 425 patients, with 601 polyps, randomized to either CSP or HSP were included in the analysis. Of 318 polyps removed by CSP and 283 polyps removed by HSP, 34 (10.7 %) and 21 (7.4 %) were incompletely resected, respectively, with an adjusted risk difference of 3.2 % (95 %CI -1.4 % to 7.8 %). There was no difference between the groups in terms of post-polypectomy bleeding, perforation, or abdominal pain. Independent risk factors for incomplete removal were serrated histology (odds ratio [OR] 3.96; 95 %CI 1.63 to 9.66) and hyperplastic histology (OR 2.52; 95 %CI 1.30 to 4.86) in adjusted analyses. Conclusion: In this randomized trial, non-inferiority for CSP could not be demonstrated. Polyps with serrated histology are more prone to incomplete resection compared with adenomas. CSP can be used safely for small polyps in routine colonoscopy practice.

• Bretthauer, Michael; Løberg, Magnus; Wieszczy, Paulina; Kalager, Mette; Emilsson, Louise & Garborg, Kjetil Kjeldstad [Show all 21 contributors for this article] (2022). Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death. New England Journal of Medicine. ISSN 0028-4793. 387(17), p. 1547–1556. doi: 10.1056/NEJMoa2208375. Full text in Research Archive Show summary

  Background: Although colonoscopy is widely used as a screening test to detect colorectal cancer, its effect on the risks of colorectal cancer and related death is unclear. Methods: We performed a pragmatic, randomized trial involving presumptively healthy men and women 55 to 64 years of age drawn from population registries in Poland, Norway, Sweden, and the Netherlands between 2009 and 2014. The participants were randomly assigned in a 1:2 ratio to either receive an invitation to undergo a single screening colonoscopy (the invited group) or to receive no invitation or screening (the usual-care group). The primary end points were the risks of colorectal cancer and related death, and the secondary end point was death from any cause. Results: Follow-up data were available for 84,585 participants in Poland, Norway, and Sweden - 28,220 in the invited group, 11,843 of whom (42.0%) underwent screening, and 56,365 in the usual-care group. A total of 15 participants had major bleeding after polyp removal. No perforations or screening-related deaths occurred within 30 days after colonoscopy. During a median follow-up of 10 years, 259 cases of colorectal cancer were diagnosed in the invited group as compared with 622 cases in the usual-care group. In intention-to-screen analyses, the risk of colorectal cancer at 10 years was 0.98% in the invited group and 1.20% in the usual-care group, a risk reduction of 18% (risk ratio, 0.82; 95% confidence interval [CI], 0.70 to 0.93). The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual-care group (risk ratio, 0.90; 95% CI, 0.64 to 1.16). The number needed to invite to undergo screening to prevent one case of colorectal cancer was 455 (95% CI, 270 to 1429). The risk of death from any cause was 11.03% in the invited group and 11.04% in the usual-care group (risk ratio, 0.99; 95% CI, 0.96 to 1.04). Conclusions: In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colonoscopy than among those who were assigned to no screening. (Funded by the Research Council of Norway and others; NordICC ClinicalTrials.gov number, NCT00883792.).

• Kalager, Mette; Adami, Hans Olov; Lagergren, Pernilla; Steindorf, Karen & Dickman, Paul W. (2021). Cancer outcomes research—a European challenge: measures of the cancer burden. Molecular Oncology. ISSN 1574-7891. 15(12), p. 3225–3241. doi: 10.1002/1878-0261.13012. Full text in Research Archive
• Kalager, Mette; Adami, Hans Olov; Dickman, Paul W.; Lagergren, Pernilla & Steindorf, Karen (2021). Cancer outcome research – a European challenge Part II: Opportunities and priorities. Molecular Oncology. ISSN 1574-7891. p. 1–12. doi: 10.1002/1878-0261.13169. Full text in Research Archive
• Mori, Yuichi; Bretthauer, Michael & Kalager, Mette (2021). Hopes and Hypes for Artificial Intelligence in Colorectal Cancer Screening. Gastroenterology. ISSN 0016-5085. 161(3), p. 774–777. doi: 10.1053/j.gastro.2021.04.078. Full text in Research Archive
• Jodal, Henriette C.; Klotz, Dagmar; Herfindal, Magnhild; Barua, Ishita; Tag, Petter & Helsingen, Lise Mørkved [Show all 12 contributors for this article] (2021). Long-term colorectal cancer incidence and mortality after adenoma removal in women and men. Alimentary Pharmacology and Therapeutics. ISSN 0269-2813. p. 1–10. doi: 10.1111/apt.16686. Full text in Research Archive
• Juul, Frederik E.; Jodal, Henriette C.; Barua, Ishita; Refsum, Erle; Olsvik, Ørjan & Helsingen, Lise Mørkved [Show all 10 contributors for this article] (2021). Mortality in Norway and Sweden during the COVID-19 pandemic. Scandinavian Journal of Public Health. ISSN 1403-4948. p. 1–8. doi: 10.1177/14034948211047137. Full text in Research Archive Show summary

  Background: Norway and Sweden are similar countries in terms of socioeconomics and health care. Norway implemented extensive COVID-19 measures, such as school closures and lockdowns, whereas Sweden did not. Aims: To compare mortality in Norway and Sweden, two similar countries with very different mitigation measures against COVID-19. <p> <p>Methods: Using real-world data from national registries, we compared all-cause and COVID-19-related mortality rates with 95% confidence intervals (CI) per 100,000 person-weeks and mortality rate ratios (MRR) comparing the five preceding years (2015–2019) with the pandemic year (2020) in Norway and Sweden. <p> <p>Results: In Norway, all-cause mortality was stable from 2015 to 2019 (mortality rate 14.6–15.1 per 100,000 person-weeks; mean mortality rate 14.9) and was lower in 2020 than from 2015 to 2019 (mortality rate 14.4; MRR 0.97; 95% CI 0.96–0.98). In Sweden, all-cause mortality was stable from 2015 to 2018 (mortality rate 17.0–17.8; mean mortality rate 17.1) and similar to that in 2020 (mortality rate 17.6), but lower in 2019 (mortality rate 16.2). Compared with the years 2015–2019, all-cause mortality in the pandemic year was 3% higher due to the lower rate in 2019 (MRR 1.03; 95% CI 1.02–1.04). Excess mortality was confined to people aged ⩾70 years in Sweden compared with previous years. The COVID-19-associated mortality rates per 100,000 person-weeks during the first wave of the pandemic were 0.3 in Norway and 2.9 in Sweden. <p> <p>Conclusions: All-cause mortality in 2020 decreased in Norway and increased in Sweden compared with previous years. The observed excess deaths in Sweden during the pandemic may, in part, be explained by mortality displacement due to the low all-cause mortality in the previous year.

• Tønnesen, Christer Julseth; Hjelmesæth, Jøran; Hofsø, Dag; Tonstad, Serena; Hertel, Jens Kristoffer & Heggen, Eli [Show all 14 contributors for this article] (2021). A novel intragastric balloon for treatment of obesity and type 2 diabetes. A two-center pilot trial. Scandinavian Journal of Gastroenterology. ISSN 0036-5521. 57(2), p. 232–238. doi: 10.1080/00365521.2021.1994641. Full text in Research Archive Show summary

  Background and aims: Obesity with type-2 diabetes is a global challenge. Lifestyle interventions have limited effect for most patients. Bariatric surgery is highly effective, but resource-demanding, invasive and associated with serious complications. Recently, a new intragastric balloon was introduced, not requiring endoscopy for placement or removal (Elipse™, Allurion Inc., Natick, MA). The balloon is swallowed in a capsule and filled with water once in the stomach. The balloon self-deflates after 4 months and is naturally excreted. The present trial investigated balloon feasibility, safety and efficacy in patients with obesity and type-2 diabetes. <p> <p>Patients and methods: We treated 19 patients, with type-2 diabetes and body mass index (BMI) of 30.0-39.9 kg/m2 at two Norwegian centers with the Elipse balloon. Patient follow-up during balloon treatment mimicked real-world clinical practice, including dietary plan and outpatient visits. The primary efficacy endpoints were total body weight loss (TBWL) and HbA1c at weeks 16 and 52. <p> <p>Results: All patients underwent balloon insertion uneventfully as out-patients. Mean TBWL and HbA1c reduction after 16 and 52 weeks of balloon insertion was 3.9% (95%CI 2.1-5.7) and 0.8% (95%CI 1.9-3.5); and 7 (95%CI 4-10), and 1 (95%CI -6 to 9) mmol/mol, respectively. Adverse events occurred in two patients (10.5%): one developed gastric outlet obstruction, managed by endoscopic balloon removal; the other excessive vomiting and dehydration, managed conservatively. <p> <p>Conclusions: This first Scandinavian real-world clinical trial with a new minimally invasive intragastric balloon system demonstrated good feasibility, but did not confirm expected efficacy for weight loss and diabetes control.

• Wieszczy, Paulina; Kaminski, Michal F; Løberg, Magnus; Bugajski, Marek; Bretthauer, Michael & Kalager, Mette (2021). Estimation of overdiagnosis in colorectal cancer screening with sigmoidoscopy and faecal occult blood testing: Comparison of simulation models. BMJ Open. 11(4), p. 1–10. doi: 10.1136/bmjopen-2020-042158. Full text in Research Archive
• Helsingen, Lise Mørkved; Løberg, Magnus; Refsum, Erle; Gjøstein, Dagrun Kyte; Wieszczy, Paulina & Olsvik, Ørjan [Show all 16 contributors for this article] (2021). Covid-19 transmission in fitness centers in Norway - a randomized trial. BMC Public Health. 21, p. 1–9. doi: 10.1186/s12889-021-12073-0. Full text in Research Archive Show summary

  Background: Closed fitness centers during the Covid-19 pandemic may negatively impact health and wellbeing. We assessed whether training at fitness centers increases the risk of SARS-CoV-2 virus infection.<p> <p>Methods: In a two-group parallel randomized controlled trial, fitness center members aged 18 to 64 without Covid-19-relevant comorbidities, were randomized to access to training at a fitness center or no-access. Fitness centers applied physical distancing (1 m for floor exercise, 2 m for high-intensity classes) and enhanced hand and surface hygiene. Primary outcomes were SARS-CoV-2 RNA status by polymerase chain reaction (PCR) after 14 days, hospital admission after 21 days. The secondary endpoint was SARS-CoV-2 antibody status after 1 month.<p> <p>Results: 3764 individuals were randomized; 1896 to the training arm and 1868 to the no-training arm. In the training arm, 81.8% trained at least once, and 38.5% trained ≥six times. Of 3016 individuals who returned the SARSCoV-2 RNA tests (80.5%), there was one positive test in the training arm, and none in the no-training arm (risk difference 0.053%; 95% CI − 0.050 to 0.156%; p = 0.32). Eleven individuals in the training arm (0.8% of tested) and 27 in the no-training arm (2.4% of tested) tested positive for SARS-CoV-2 antibodies (risk difference − 0.87%; 95%CI − 1.52% to − 0.23%; p = 0.001). No outpatient visits or hospital admissions due to Covid-19 occurred in either arm.<p> <p>Conclusion: Provided good hygiene and physical distancing measures and low population prevalence of SARS-CoV-2 infection, there was no increased infection risk of SARS-CoV-2 in fitness centers in Oslo, Norway for individuals without Covid-19-relevant comorbidities.

• Wieszczy, Paulina; Waldmann, Elisabeth; Løberg, Magnus; Regula, Jaroslaw; Rupinski, Maciej & Bugajski, Marek [Show all 11 contributors for this article] (2021). Colonoscopist Performance and Colorectal Cancer Risk After Adenoma Removal to Stratify Surveillance: Two Nationwide Observational Studies. Gastroenterology. ISSN 0016-5085. 160(4), p. 1067–1074.e6. doi: 10.1053/j.gastro.2020.10.009. Full text in Research Archive
• Helsingen, Lise M.; Refsum, Erle; Gjøstein, Dagrun Kyte; Løberg, Magnus; Bretthauer, Michael & Kalager, Mette [Show all 7 contributors for this article] (2020). The COVID-19 pandemic in Norway and Sweden – threats, trust, and impact on daily life: a comparative survey. BMC Public Health. 20:1597, p. 1–10. doi: 10.1186/s12889-020-09615-3. Full text in Research Archive Show summary

  Background Norway and Sweden have similar populations and health care systems, but different reactions to the COVID-19 pandemic. Norway closed educational institutions, and banned sports and cultural activities; Sweden kept most institutions and training facilities open. We aimed to compare peoples’ attitudes towards authorities and control measures, and perceived impact of the pandemic and implemented control measures on life in Norway and Sweden. Methods Anonymous web-based surveys for individuals age 15 or older distributed through Facebook using the snowball method, in Norway and Sweden from mid-March to mid-April, 2020. The survey contained questions about perceived threat of the pandemic, views on infection control measures, and impact on daily life. We performed descriptive analyses of the responses and compared the two countries. Results 3508 individuals participated in the survey (Norway 3000; Sweden 508). 79% were women, the majority were 30–49 years (Norway 60%; Sweden 47%), and about 45% of the participants in both countries had more than 4 years of higher education. Participants had high trust in the health services, but differed in the degree of trust in their government (High trust in Norway 17%; Sweden 37%). More Norwegians than Swedes agreed that school closure was a good measure (Norway 66%; Sweden 18%), that countries with open schools were irresponsible (Norway 65%; Sweden 23%), and that the threat from repercussions of the mitigation measures were large or very large (Norway 71%; Sweden 56%). Both countries had a high compliance with infection preventive measures (> 98%). Many lived a more sedentary life (Norway 69%; Sweden 50%) and ate more (Norway 44%; Sweden 33%) during the pandemic. Conclusion Sweden had more trust in the authorities, while Norwegians reported a more negative lifestyle during the pandemic. The level of trust in the health care system and self-reported compliance with preventive measures was high in both countries despite the differences in infection control measures.

• Adami, Hans Olov; Bretthauer, Michael & Kalager, Mette (2020). Assessment of cancer screening effectiveness in the era of screening programs. European Journal of Epidemiology (EJE). ISSN 0393-2990. doi: 10.1007/s10654-020-00684-7. Full text in Research Archive
• Berns, Anton; Ringborg, Ulrik; Celis, Julio E.; Heitor, Manuel; Aaronson, Neil K. & Abou-Zeid, Nancy [Show all 41 contributors for this article] (2020). Towards a cancer mission in Horizon Europe: recommendations. Molecular Oncology. ISSN 1574-7891. 14(8), p. 1589–1615. doi: 10.1002/1878-0261.12763. Full text in Research Archive
• Lousdal, Mette Lise; Lash, Timothy L.; Flanders, W Dana; Brookhart, M Alan; Kristiansen, Ivar Sønbø & Kalager, Mette [Show all 7 contributors for this article] (2020). Negative controls to detect uncontrolled confounding in observational studies of mammographic screening comparing participants and non-participants. International Journal of Epidemiology. ISSN 0300-5771. 49(3), p. 1032–1042. doi: 10.1093/ije/dyaa029. Full text in Research Archive
• Barua, Ishita; Vinsard, Daniela Guerrero; Jodal, Henriette C.; Løberg, Magnus; Kalager, Mette & Holme, Øyvind [Show all 9 contributors for this article] (2020). Artificial intelligence for polyp detection during colonoscopy: A systematic review and meta-analysis. Endoscopy. ISSN 0013-726X. doi: 10.1055/a-1201-7165. Full text in Research Archive
• Hassan, Cesare; Antonelli, Giulio; Dumonceau, Jean-Marc; Regula, Jaroslaw; Bretthauer, Michael & Chaussade, Stanislas [Show all 21 contributors for this article] (2020). Post-polypectomy colonoscopy surveillance: European Society of Gastrointestinal Endoscopy (ESGE) Guideline - Update 2020. Endoscopy. ISSN 0013-726X. 52(8), p. 687–700. doi: 10.1055/a-1185-3109. Full text in Research Archive
• Pedersen, Ina Borgenheim; Bretthauer, Michael; Kalager, Mette; Løberg, Magnus; Hoff, Geir & Matapour, Senaria [Show all 13 contributors for this article] (2020). Incomplete endoscopic resection of colorectal polyps: a prospective quality assurance study. Endoscopy. ISSN 0013-726X. p. 1–9. doi: 10.1055/a-1243-0379. Full text in Research Archive
• Helsingen, Lise M.; Vandvik, Per Olav; Jodal, Henriette C.; Agoritsas, Thomas; Lytvyn, Lyubov & Anderson, Joseph C. [Show all 21 contributors for this article] (2019). Colorectal cancer screening with faecal immunochemical testing, sigmoidoscopy or colonoscopy: A clinical practice guideline. The BMJ. 367:I5515, p. 1–16. doi: 10.1136/bmj.l5515. Full text in Research Archive Show summary

  Abstract CLINICAL QUESTION: Recent 15-year updates of sigmoidoscopy screening trials provide new evidence on the effectiveness of colorectal cancer screening. Prompted by the new evidence, we asked: "Does colorectal cancer screening make an important difference to health outcomes in individuals initiating screening at age 50 to 79? And which screening option is best?" CURRENT PRACTICE: Numerous guidelines recommend screening, but vary on recommended test, age and screening frequency. This guideline looks at the evidence and makes recommendations on screening for four screening options: faecal immunochemical test (FIT) every year, FIT every two years, a single sigmoidoscopy, or a single colonoscopy. RECOMMENDATIONS: These recommendations apply to adults aged 50-79 years with no prior screening, no symptoms of colorectal cancer, and a life expectancy of at least 15 years. For individuals with an estimated 15-year colorectal cancer risk below 3%, we suggest no screening (weak recommendation). For individuals with an estimated 15-year risk above 3%, we suggest screening with one of the four screening options: FIT every year, FIT every two years, a single sigmoidoscopy, or a single colonoscopy (weak recommendation). With our guidance we publish the linked research, a graphic of the absolute harms and benefits, a clear description of how we reached our value judgments, and linked decision aids. HOW THIS GUIDELINE WAS CREATED: A guideline panel including patients, clinicians, content experts and methodologists produced these recommendations using GRADE and in adherence with standards for trustworthy guidelines. A linked systematic review of colorectal cancer screening trials and microsimulation modelling were performed to inform the panel of 15-year screening benefits and harms. The panel also reviewed each screening option's practical issues and burdens. Based on their own experience, the panel estimated the magnitude of benefit typical members of the population would value to opt for screening and used the benefit thresholds to inform their recommendations. THE EVIDENCE: Overall there was substantial uncertainty (low certainty evidence) regarding the 15-year benefits, burdens and harms of screening. Best estimates suggested that all four screening options resulted in similar colorectal cancer mortality reductions. FIT every two years may have little or no effect on cancer incidence over 15 years, while FIT every year, sigmoidoscopy, and colonoscopy may reduce cancer incidence, although for FIT the incidence reduction is small compared with sigmoidoscopy and colonoscopy. Screening related serious gastrointestinal and cardiovascular adverse events are rare. The magnitude of the benefits is dependent on the individual risk, while harms and burdens are less strongly associated with cancer risk. UNDERSTANDING THE RECOMMENDATION: Based on benefits, harms, and burdens of screening, the panel inferred that most informed individuals with a 15-year risk of colorectal cancer of 3% or higher are likely to choose screening, and most individuals with a risk of below 3% are likely to decline screening. Given varying values and preferences, optimal care will require shared decision making.

• Seppälä, Toni T.; Ahadova, Aysel; Dominguez-Valentin, Mev; Macrae, Finlay; Evans, D. Gareth & Therkildsen, Christina [Show all 57 contributors for this article] (2019). Lack of association between screening interval and cancer stage in Lynch syndrome may be accounted for by over-diagnosis; A prospective Lynch syndrome database report. Hereditary Cancer in Clinical Practice. ISSN 1731-2302. 17:8, p. 1–8. doi: 10.1186/s13053-019-0106-8. Full text in Research Archive Show summary

  Background Recent epidemiological evidence shows that colorectal cancer (CRC) continues to occur in carriers of pathogenic mismatch repair (path_MMR) variants despite frequent colonoscopy surveillance in expert centres. This observation conflicts with the paradigm that removal of all visible polyps should prevent the vast majority of CRC in path_MMR carriers, provided the screening interval is sufficiently short and colonoscopic practice is optimal. Methods To inform the debate, we examined, in the Prospective Lynch Syndrome Database (PLSD), whether the time since last colonoscopy was associated with the pathological stage at which CRC was diagnosed during prospective surveillance. Path_MMR carriers were recruited for prospective surveillance by colonoscopy. Only variants scored by the InSiGHT Variant Interpretation Committee as class 4 and 5 (clinically actionable) were included. CRCs detected at the first planned colonoscopy, or within one year of this, were excluded as prevalent cancers. Results Stage at diagnosis and interval between last prospective surveillance colonoscopy and diagnosis were available for 209 patients with 218 CRCs, including 162 path_MLH1, 45 path_MSH2, 10 path_MSH6 and 1 path_PMS2 carriers. The numbers of cancers detected within < 1.5, 1.5–2.5, 2.5–3.5 and at > 3.5 years since last colonoscopy were 36, 93, 56 and 33, respectively. Among these, 16.7, 19.4, 9.9 and 15.1% were stage III–IV, respectively (p = 0.34). The cancers detected more than 2.5 years after the last colonoscopy were not more advanced than those diagnosed earlier (p = 0.14). Conclusions The CRC stage and interval since last colonoscopy were not correlated, which is in conflict with the accelerated adenoma-carcinoma paradigm. We have previously reported that more frequent colonoscopy is not associated with lower incidence of CRC in path_MMR carriers as was expected. In contrast, point estimates showed a higher incidence with shorter intervals between examinations, a situation that may parallel to over-diagnosis in breast cancer screening. Our findings raise the possibility that some CRCs in path_MMR carriers may spontaneously disappear: the host immune response may not only remove CRC precursor lesions in path_MMR carriers, but may remove infiltrating cancers as well. If confirmed, our suggested interpretation will have a bearing on surveillance policy for path_MMR carriers.

• Wieszczy, Paulina; Kamiński, Michał Filip; Franczyk, Robert; Løberg, Magnus; Kobiela, Jarek & Rupinska, Maria [Show all 15 contributors for this article] (2019). Colorectal Cancer Incidence and Mortality After Removal of Adenomas During Screening Colonoscopies. Gastroenterology. ISSN 0016-5085. 158(4), p. 875–883. doi: 10.1053/j.gastro.2019.09.011. Full text in Research Archive
• Bleijenberg, Arne; Klotz, Dagmar; Løberg, Magnus; Dekker, Evelien; Adami, Hans Olov & Kuipers, Ernst J. [Show all 15 contributors for this article] (2019). Implications of different guidelines for surveillance after serrated polyp resection in United States of America and Europe. Endoscopy. ISSN 0013-726X. 51(8), p. 750–758. doi: 10.1055/a-0916-8598. Full text in Research Archive
• Zahl, Per Henrik; Kalager, Mette; Suhrke, Pål & Nord, Erik (2019). Quality-of-life effects of screening mammography in Norway. International Journal of Cancer. ISSN 0020-7136. doi: 10.1002/ijc.32539. Full text in Research Archive Show summary

  Mammography screening may save women from dying of breast cancer, although it has not been shown to reduce all-cause mortality. Screening also leads to overdiagnosis and many false positive mammograms aggravating women's quality-of-life. Quality adjusted life years (QALY) analyses of mammography screening have so far, calculated life years gained assuming that all prevented breast cancer deaths translate into a reduction in all-cause mortality. We calculated net QALYs in two hypothesized cohorts of 100,000 Norwegian women; one screened biennially from age 50 to 69 years and one not screened. We followed both cohorts to age 85 years. We used EQ-5D and an alternative equity weighted QALY instrument to estimate utility losses. In the screening cohort, we assumed 20% false positive tests during screening, different levels of overdiagnosis (20-75%) and different levels of breast cancer mortality reduction (10-30%). We assumed that reductions in breast cancer mortality only to a limited extent (20, 50 or 80%), resulted in reductions in all-cause mortality. We calculated both undiscounted and discounted (4%) QALYs. Assuming that 50% of the reduction in breast cancer mortality translated to a reduction in all-cause mortality and using estimated levels of benefits and harms in modern screening programs (50-75% overdiagnosis and 10% reduction in breast cancer mortality), undiscounted equity weighted QALY loss varied from 437 to 875 per 100,000 women. Using the levels of benefit and harms as reported in 30-40 years old randomized trials (30% overdiagnosis and 15% reduction in breast cancer mortality), undiscounted equity weighted QALY gain was 535 per 100,000. Net QALY in modern mammography screening in Norway is negative. Results could also be representative for Sweden, Denmark, UK and the US.

• Emilsson, Louise; García-Albéniz, Xabier; Logan, Roger W.; Caniglia, E.C.; Kalager, Mette & Hernan, Miguel A. (2018). Examining Bias in Studies of Statin Treatment and Survival in Patients With Cancer. JAMA Oncology. ISSN 2374-2437. 4(1), p. 63–70. doi: 10.1001/jamaoncol.2017.2752. Full text in Research Archive
• Lousdal, Mette Lise; Møller, Mette H.; Kristiansen, Ivar Sønbø; Kalager, Mette; Wisløff, Torbjørn & Støvring, Henrik (2018). The Screening Illustrator: separating the effects of lead-time and overdiagnosis in mammography screening. European Journal of Public Health. ISSN 1101-1262. 28(6), p. 1138–1142. doi: 10.1093/eurpub/cky085. Full text in Research Archive
• Kalager, Mette; Wieszczy, Paulina; Lansdorp-Vogelaar, I; Corley, Douglas; Bretthauer, Michael & Kamiński, Michał Filip (2018). Overdiagnosis in Colorectal Cancer Screening: Time to Acknowledge a Blind Spot. Gastroenterology. ISSN 0016-5085. 155(3), p. 592–595. doi: 10.1053/j.gastro.2018.07.037. Full text in Research Archive
• Adami, Hans Olov; Kalager, Mette; Valdimarsdottir, U; Bretthauer, Michael & Ioannidis, JPA (2018). Time to abandon early detection cancer screening. European Journal of Clinical Investigation. ISSN 0014-2972. 49(3). doi: 10.1111/eci.13062. Full text in Research Archive
• Bretthauer, Michael; Goderstad, Jeanne Mette; Løberg, Magnus; Emilsson, Louise; Ye, Weimin & Adami, Hans Olov [Show all 7 contributors for this article] (2018). Uterine morcellation and survival in uterine sarcomas. European Journal of Cancer. ISSN 0959-8049. 101, p. 62–68. doi: 10.1016/j.ejca.2018.06.007. Full text in Research Archive

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• Kalager, Mette; Bretthauer, Michael; Graver, Hans Petter; Helsingen, Lise Mørkved; Løberg, Magnus & Nylund, Anna [Show all 7 contributors for this article] (2025). Forholdsmessighet. Medisin, juss, filosofi og pandemi. Fagbokforlaget. ISBN 9788245053555. 348 p. Full text in Research Archive

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• Kanjee, Zahir; Wong, John B.; Kalager, Mette & Burns, Risa B. (2025). When Would You Screen This 39-Year-Old Woman for Breast Cancer? Grand Rounds Discussion From Beth Israel Deaconess Medical Center. Annals of Internal Medicine. ISSN 0003-4819. 178(10), p. 1478–1486. doi: 10.7326/ANNALS-25-03548. Full text in Research Archive
• Helsingen, Lise Mørkved; Langeland, Eline Aurvoll; Pisani, Synne Eline Rotihaug; Vandvik, Per Olav; Haavardsholm, Espen A. & Malt, Ulrik Fredrik [Show all 10 contributors for this article] (2024). Glansbilder av nasjonale faglige retningslinjer fra Helsedirektoratet. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 144(5). doi: 10.4045/tidsskr.24.0141. Full text in Research Archive
• Juul, Frederik Emil; Bretthauer, Michael; Tonby, Kristian; Berdal, Jan-Erik; Hoff, Dag Arne Lihaug & Ofstad, Eirik Hugaas [Show all 27 contributors for this article] (2024). Fecal microbiota transplant versus Vancomycin for primary Clostridioides difficile infection - a randomized non-inferiority trial. Full text in Research Archive
• Bretthauer, Michael; Kaminski, Michal F. & Kalager, Mette (2024). Lifetime Gained with Cancer Screening - Reply. JAMA Internal Medicine. ISSN 2168-6106. doi: 10.1001/jamainternmed.2023.7067. Full text in Research Archive
• Gantzel, Rasmus; Wieszczy, Paulina; Refsum, Erle; Jess, Tine; Larsen, Lone & Bretthauer, Michael [Show all 11 contributors for this article] (2023). Prognostic models for colorectal cancer incidence and mortality in patients with inflammatory bowel disease. Cochrane Database of Systematic Reviews. doi: 10.1002/14651858.CD015434. Full text in Research Archive
• Øverenget, Einar; Kalager, Mette; Grødeland, Gunnveig; Olsvik, Ørjan; Nylund, Anna & Løberg, Magnus [Show all 8 contributors for this article] (2022). Når smittevern blir uforståelig. Full text in Research Archive
• Jodal, Henriette C.; Bretthauer, Michael; Kalager, Mette & Løberg, Magnus (2022). Letter: long-term colorectal cancer incidence and mortality after adenoma removal associated with heritable factors, colonoscopic surveillance and aspirin—authors' reply. Alimentary Pharmacology and Therapeutics. ISSN 0269-2813. 55(10), p. 1363–1364. doi: 10.1111/apt.16929. Full text in Research Archive
• Helsingen, Lise Mørkved; Løberg, Magnus; Bretthauer, Michael & Kalager, Mette (2022). Reply to: Letter to the Editor regarding "Covid-19 transmission in fitness centers in Norway-a randomized trial". BMC Public Health. 22(1), p. 2437–2437. doi: 10.1186/s12889-022-14799-x. Full text in Research Archive
• Grødeland, Gunnveig; Fossum, Even & Kalager, Mette (2022). Smittevernstiltak. [Radio]. Vaksinepodden. Full text in Research Archive
• Bretthauer, Michael; Kalager, Mette & Weinberg, David S. (2021). Colorectal cancer screening in young adults: About carcinoid tumors and cancer. Annals of Internal Medicine. ISSN 0003-4819. 174(2), p. 263–265. doi: 10.7326/M20-7244. Full text in Research Archive
• Bretthauer, Michael; Løberg, Magnus; Holme, Øyvind; Adami, Hans-Olov & Kalager, Mette (2021). Deep learning and cancer biomarkers: recognising lead-time bias. The Lancet. ISSN 0140-6736. 397(10270), p. 194–194. doi: 10.1016/S0140-6736(20)32402-8. Full text in Research Archive
• Bretthauer, Michael; Helsingen, Lise Mørkved; Kalager, Mette; Vandvik, Per Olav; Agoritsas, Thomas & Guyatt, Gordon (2020). The future of colorectal cancer screening: Parentalism or shared decision-making? CMAJ - Canadian Medical Association Journal. ISSN 0820-3946. 192(18), p. E484–E484. doi: 10.1503/cmaj.74839. Full text in Research Archive
• Bretthauer, Michael & Kalager, Mette (2020). Disparities in preventive health services: Targeting minorities and majorities. Annals of Internal Medicine. ISSN 0003-4819. 172(4), p. 287–288. doi: 10.7326/M19-3899. Full text in Research Archive
• Rutter, Matthew D.; Bretthauer, Michael; Hassan, Cesare; Jover, Rodrigo; Adami, Hans-Olov & Corley, Douglas A. [Show all 20 contributors for this article] (2020). Principles for Evaluation of Surveillance After Removal of Colorectal Polyps: Recommendations From the World Endoscopy Organization. Gastroenterology. ISSN 0016-5085. 158(6), p. 1529–1533.e4. doi: 10.1053/j.gastro.2019.12.052. Full text in Research Archive
• Zahl, Per Henrik & Kalager, Mette (2020). Reply to: Loss of QALY in mammography screening reported by Zahl et al. International Journal of Cancer. ISSN 0020-7136. 146(4), p. 1177–1177. doi: 10.1002/ijc.32755. Full text in Research Archive
• Brinchmann, Bendik Christian; Dietrichs, Erik Sveberg; Haavardsholm, Espen A. & Kalager, Mette (2020). Leger som forsker er navet i kunnskapsbasert medisin. Full text in Research Archive
• Kalager, Mette & Bretthauer, Michael (2020). Improving cancer screening programs: Evaluating diagnostic tests in learning screening programs could improve public health. 367(6474), p. 143–144. doi: 10.1126/science.aay3156. Full text in Research Archive
• Refsum, Erle; Helsingen, Lise M.; Jodal, Henriette Cecilie; Løberg, Magnus; Høstmælingen, Njål & Kalager, Mette (2019). Personvern – en hinderløype. 139(4), p. 1–3. doi: 10.4045/tidsskr.19.0077. Full text in Research Archive
• Holme, Øyvind; Bretthauer, Michael; Løberg, Magnus; Kalager, Mette & Adami, Hans Olov (2019). Revisiting surveillance schemes for cancer survivors. Annals of Oncology. ISSN 0923-7534. 30(6), p. 881–883. doi: 10.1093/annonc/mdz107. Full text in Research Archive
• Adami, Hans Olov; Kalager, Mette; Valdimarsdottir, Unnur; Bretthauer, Michael & Ioannidis, John P.A. (2019). Author Reply to: The name of the game: Is preventive screening ?cancer screening?? European Journal of Clinical Investigation. ISSN 0014-2972. 49(6). doi: 10.1111/eci.13097. Full text in Research Archive
• Kalager, Mette (2019). StatMed - den nye oljen? Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 139(9). doi: 10.4045/tidsskr.19.0349. Full text in Research Archive
• Holme, Øyvind; Bretthauer, Michael; Løberg, Magnus; Kalager, Mette & Adami, Hans-Olov (2019). Reply to the letter to the editor 'Cancer survivors: Surveillance or not surveillance?' by Santeufemia and Miolo. Annals of Oncology. ISSN 0923-7534. 30(9), p. 1532–1532. doi: 10.1093/annonc/mdz190. Full text in Research Archive
• Helsingen, Lise M.; Vandvik, Per Olav; Jodal, Henriette C.; Murphy, Silje Bjerkelund; Heen, Anja Fog & Kalager, Mette [Show all 7 contributors for this article] (2019). Tarmkreftscreening, eller ikke? 139(15). doi: 10.4045/tidsskr.19.0323. Full text in Research Archive
• Løberg, Magnus; Kalager, Mette & Hoff, Geir (2018). Tailoring the message with selective reporting. European Journal of Epidemiology (EJE). ISSN 0393-2990. doi: 10.1007/s10654-018-0416-6. Full text in Research Archive
• Kalager, Mette & Bretthauer, Michael (2018). When no guideline recommendation is the best recommendation. The Lancet. ISSN 0140-6736. 392(10151), p. 898–899. doi: 10.1016/S0140-6736(18)31671-4. Full text in Research Archive
• Kalager, Mette (2018). Helse uten kunnskap? p. 138–138. doi: 10.4045/tidsskr.17.12.024. Full text in Research Archive
• Bretthauer, Michael; Kalager, Mette & Weinberg, David S. (2018). From Colorectal Cancer Screening Guidelines to Headlines: Beware! Annals of Internal Medicine. ISSN 0003-4819. 170(10), p. 733–740. doi: 10.7326/L19-0086. Full text in Research Archive
• Kwiatkowska, Anna; Jong, Aurora de; Ajer, Camilla E.; Grimstad, Fredrik G.; Borch, Pernille & Øverbø, Simen Lunderød [Show all 7 contributors for this article] (2026). Økt mobilisering av pasienter innlagt på akuttgeriatrisk sengepost. Universitetet i Oslo. Full text in Research Archive
• Al-Rammahy, Afaf; Hussain, Aiza; Nyberg, Daniel; Boateng, Marcus Juliussen; Fjordbo, Oline & Nyikach, Peter [Show all 8 contributors for this article] (2026). Fra surt til skånsomt: innføring av bufret lidokain for mindre injeksjonssmerte ved Skadelegevakten i Oslo. Universitetet i Oslo. Full text in Research Archive
• Juel-Karlstad, Kristoffer B.; Berntsen, Sanna Strand; Bugge, Vilhelm; Chaudry, Talha Solhail; Corbett, Rebecca Aure & Mahamud, Dhudi [Show all 8 contributors for this article] (2026). Tidlig introduksjon av allergener for forebygging av matvareallergi hos spedbarn. Universitetet i Oslo. Full text in Research Archive

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