Sensitivity of fecal immunochemical test and risk factors for interval colorectal cancer in a French population

Abstract

Background: Colorectal cancer (CRC) screening using fecal immunochemical testing (FIT) aims to detect pre-symptomatic colorectal lesions and reduce CRC mortality.

Aims: The objectives of this study were to determine the FIT sensitivity for diagnosis of CRC, the impact of diagnostic circumstances on treatment and survival, and risk factors for interval cancer (IC).

Methods: This population-based study evaluated the 2016-2017 CRC screening campaign in Finistère, France. CRCs were classified according to diagnostic circumstances: screen-detected CRC (SD-CRC), CRC with delayed diagnosis, IC after negative FIT (FIT-IC), post-colonoscopy CRC, CRC in non-responders and CRC in the excluded population.

Results: This study included 909 CRCs: 248 SD-CRCs (6% of positive FIT) and 60 FIT-ICs (0.07% of negative FIT). The FIT sensitivity for CRC was 80.5% (CI95%: 76.1-84.9) at the threshold of 30 µg hemoglobin/g feces used in France. In multivariate analysis, proximal (OR:6.73) and rectal locations (OR:7.52) were associated with being diagnosed with FIT-IC rather than SD-CRC. The FIT positivity threshold maximizing the sum of sensitivity and specificity was found to be 17 µg/g, with 14 additional CRCs diagnosed compared to the current threshold.

Conclusions: Our study confirms the good sensitivity of FIT. A decrease of the FIT detection threshold could optimize sensitivity.

Keywords: Colorectal cancer; Fecal immunochemical test; Interval cancer; Screening.