Factors associated with interval colorectal cancer after negative FIT: Results of two screening rounds in the Dutch FIT-based CRC screening program

The interval colorectal cancer (CRC) rate after negative fecal immunochemical testing (FIT) is an important quality indicator of CRC screening programs. We analyzed the outcomes of two rounds of the FIT-based CRC screening program in the Netherlands, using data from individuals who participated in FIT-screening from 2014 to 2017. Data of individuals with one prior negative FIT (first round) or two prior negative FITs (first and second round) were included. Outcomes included the incidence of interval CRC in FIT-negative participants (<47 μg Hb/g feces [μg/g]), FIT-sensitivity, and the probability of detecting an interval CRC by fecal hemoglobin concentration (f-Hb). FIT-sensitivity was estimated using the detection method and the proportional incidence method (based on expected CRC incidence). Logistic regression analysis was performed to estimate whether f-Hb affects probability of detecting interval CRC, adjusted for sex- and age-differences. Incidence of interval CRC was 10.4 per 10 000 participants after the first and 9.6 after the second screening round. FIT-sensitivity based on the detection method was 84.4% (95%CI 83.8-85.0) in the first and 73.5% (95% CI 71.8-75.2) in the second screening round. The proportional incidence method resulted in a FIT-sensitivity of 76.4% (95%CI 73.3-79.6) in the first and 79.1% (95%CI 73.7-85.3) in the second screening round. After one negative FIT, participants with f-Hb just below the cut-off (>40-46.9 μg/g) had a higher probability of detecting an interval CRC (OR 16.9; 95%CI: 14.0-20.4) than had participants with unmeasurable f-Hb (0-2.6 μg/g). After two screening rounds, the odds ratio for interval CRC was 12.0 (95%CI: 7.8-17.6) for participants with f-Hb just below the cut-off compared with participants with unmeasurable f-Hb. After both screening rounds, the Dutch CRC screening program had a low incidence of interval CRC and an associated high FIT-sensitivity. Our findings suggest there is a potential for further optimizing CRC screening programs with the use of risk-stratified CRC screening based on prior f-Hb.