Many national and international health organisations demand evidence from randomised trials to reduce incidence or mortality of the target disease before advocating population-wide cancer screening. However, while colonoscopy screening for the prevention of colorectal cancer is established in the United States and several European countries, no randomised trials exist to quantify the possible benefit of colonoscopy screening. NordICC is the first randomised trial investigating the effect of colonoscopy on CRC incidence and mortality
Incidence, risk and prognosis for CRC
Approximately 85% of all CRCs are sporadic, i.e. occurring outside defined high-risk groups. The risk for developing this type of cancer increases with age. Symptoms often emerge at a late stage of the disease and are non-specific. The prognosis of CRC diagnosed at a symptomatic stage is poor and does not exceed a 5-year survival of 50% in most countries. Early diagnosis is crucial since treatment in an early stage is the only option for cure and a major reason for recommending CRC screening in an increasing number of countries (2, 3 & 4).
Precursor lesions
Most cases of CRC (60-90%) develop from wart-like outgrowths of the colonic mucosa (adenomas or adenomatous polyps). It is estimated that it takes on average 10 years from a detectable adenoma until it has evolved into cancer. Thus, the removal of adenomas may prevent cancer. Adenomas are common in the Nordic and European average-risk population (up to 25% of healthy 50-year-olds and 50% of healthy 70-year-olds). For this reason, many health providers considering CRC screening focus not only on screening methods that can detect CRC but also adenoma detection.