Overdiagnosis in Colorectal Cancer Screening?

Overdiagnosis is recognized as a major harm of mammography and prostate cancer screening – what about colorectal cancer screening?

Colorectal cancer screening is currently implemented in many countries, but surprisingly, there is a lack of knowledge about overdiagnosis in colorectal cancer screening. Overdiagnosis in colorectal cancer screening is not mentioned in patient information or guidelines, and not addressed in scientific or public debate.

Proposes future framework

Mette Kalager and colleagues from the University of Oslo and Oslo University Hospital address this emerging topic together with other leaders in screening from the United States, the Netherlands, and Poland in a new paper in Gastroenterology, the leading journal of the field.

The paper Overdiagnosis in Colorectal Cancer Screening: Time to Acknowledge a Blind Spot outlines a semantic, conceptual and clinical framework for overdiagnosis in CRC screening. The authors argue that there indeed is overdiagnosis of polyps in colorectal cancer screening. This may be related to relatively little harm for the patient, but it occurs in large numbers. The authors continue to explain why overdiagnosis for cancer may occur also in colorectal cancer screening, even though screening reduces cancer incidence. The paper is the first to address this important topic, and it is expected to open the field for research.


New conceptual framework for overdiagnosis in colorectal cancer screening

Colorectal cancer incidence curves for early detection screening tests illustrating overdiagnosis (dotted blue line) and for prevention tests with overdiagnosis (dashed green line), compared to no-screening. As illustrated, the curves for the prevention test also includes early detection of cancers as is the case with endoscopic screening for colorectal cancer. The amount of overdiagnosis for early detection tests is the difference between the dotted blue line and the black line, blue highlighted area between the curves. The amount of overdiagnosis for prevention tests is the difference between the dashed green line and the whole green line, green highlighted area between the curves. The figure is illustrative of concepts and is not meant to infer specific known magnitudes of effect.


Tags: colorectal cancer, screening, overdiagnosis By Anita Aalby
Published Aug. 15, 2018 10:49 AM - Last modified Sep. 11, 2018 2:19 PM