Colorectal cancer screening with repeated fecal immunochemical test versus sigmoidoscopy: baseline results from a randomized trial

Background and aims: The comparative effectiveness of sigmoidoscopy and fecal immunochemical testing (FIT) for colorectal cancer (CRC) screening is unknown. Methods: Individuals aged 50-74 years living in South-East Norway were randomly invited between 2012 and 2019 to either once-only flexible sigmoidoscopy or FIT screening every second year. Colonoscopy was recommended after sigmoidoscopy if any polyp ≥10 mm, ≥ three adenomas, any advanced adenomas, or CRC was found or subsequent to FIT > 15 μg hemoglobin/g feces. Data for this report were obtained after complete recruitment in both groups and included two full FIT rounds and part of the third round. Outcome measures were participation, neoplasia detection, and adverse events. Age-standardized detection rates and age-adjusted odds ratios (OR) were calculated. Results: We included 139,291 individuals; 69,195 randomized to sigmoidoscopy and 70,096 to FIT. Participation rate was 52% for sigmoidoscopy, 58% in the first FIT round and 68% for three cumulative FIT rounds. Compared to sigmoidoscopy, detection rate for CRC was similar in the first FIT round (0.25% vs 0.27%, OR 0.92, 95% CI 0.75-1.13), but higher after three FIT rounds (0.49% vs 0.27%, OR 1.87, 95% CI 1.54-2.27). Advanced adenoma detection rate was lower in the first FIT round compared to sigmoidoscopy, 1.4% vs 2.4% (OR 0.57, 95% CI 0.53-0.62), but higher after three cumulative FIT rounds, 2.7% vs 2.4% (OR 1.14, 95% CI 1.05-1.23). There were 33 (0.05%) serious adverse events in the sigmoidoscopy group compared to 47 (0.07%) in the FIT group (p =.13). Conclusion: Participation was higher and more CRC and advanced adenomas were detected with repeated FIT compared to sigmoidoscopy. The risk of perforation and bleeding was comparable. Clinicaltrials.gov (NCT01538550).