Mortality From Postscreening (Interval) Colorectal Cancers Is Comparable to That From Cancer in Unscreened Patients—A Randomized Sigmoidoscopy Trial

Background & Aims Endoscopic screening for colorectal cancer (CRC) is performed at longer time intervals than the fecal occult blood test or screenings for breast or prostate cancer. This causes concerns about interval cancers, which have been proposed to progress more rapidly. We compared outcomes of patients with interval CRCs after sigmoidoscopy screening vs outcomes of patients with CRC who had not been screened. Methods We performed a secondary analysis of a randomized sigmoidoscopy screening trial in Norway with 98,684 participants (age range, 50–64 years) who were randomly assigned to groups that were (n = 20,552) or were not (n = 78,126) invited for sigmoidoscopy screening from 1999 through 2001; participants were followed up for a median 14.8 years. We compared CRC mortality and all-cause mortality between individuals who underwent screening and were diagnosed with CRC 30 days or longer after screening (interval cancer group, n = 163) and individuals diagnosed with CRC in the nonscreened group (controls, n = 1740). All CRCs in the control group were identified when they developed symptoms (clinically detected CRCs). Analyses were stratified by cancer site. We used Cox regression to estimate hazard ratio (HRs), adjusted for age and sex. Results Over the follow-up period, 43 individuals in the interval cancer group died from CRC; among controls, 525 died from CRC. CRC mortality (adjusted HR, 0.98; 95% confidence interval, 0.72–1.35; P = .92), rectosigmoid cancer mortality (adjusted HR, 1.10; 95% confidence interval, 0.63–1.92; P = .74), and all-cause mortality (adjusted HR, 0.99; 95% confidence interval, 0.76–1.27; P = .91) did not differ significantly between the interval cancer group and controls. Conclusions In this randomized sigmoidoscopy screening trial, mortality did not differ significantly between individuals with interval CRCs and unscreened patients with clinically detected CRCs. ClinicalTrials.gov identifier: NCT00119912 .