Proportional incidence of interval colorectal cancer in a large population-based faecal immunochemical test screening programme

Background: The European guidelines for quality assurance in colorectal cancer (CRC) screening recommend that interval cancer rate be expressed as a proportion of background incidence rate.

Aim: To determine the crude and adjusted proportional incidence of interval CRC in an Italian regional two-yearly faecal immunochemical test (FIT) screening programme.

Methods: The programme (year of implementation, 2005) is targeted at over 1,000,000 people aged 50-69 years. The test is a one-sample OC-Sensor (Eiken Chemical Co., Tokyo, Japan). The study covered one-third of the regional area. Excerpts of 434,295 eligible negative FIT records dated 2005-2012 from 193,193 subjects were retrieved from the regional CRC screening data warehouse. By 31 December 2013, the cohort accumulated 198,302 man-years and 235,370 woman-years. Interval CRCs were identified by record-linkage with the local population-based cancer registry. Their number was divided by the expected number, estimated with age-period-cohort models, to obtain the proportional incidence.

Results: The proportional incidence of interval CRC for men and women was, respectively, 0.06 (95% confidence interval (CI), 0.04-0.09) and 0.17 (95% CI, 0.13-0.23) in the first interval year, and 0.21 (95% CI, 0.16-0.26) and 0.28 (95% CI, 0.22-0.36) in the second year.

Conclusions: The results were acceptable and in line with previous studies.