INTERVAL COLORECTAL CANCERS AFTER NEGATIVE FECAL IMMUNOCHEMICAL TEST IN A 13-YEAR SCREENING PROGRAM

Aims:

Interval cancers (IC) were considered in order to judge the round-specific sensitivity of fecal immunochemical tests (FIT) within a colorectal cancer screening program in Italy.

Methods:

This study concerns ICs diagnosed in a cohort of 50- to 69-year-olds screened with FIT repeatedly (up to 6 times) between 2002 and 2015. The test's sensitivity was calculated using both the Proportional Interval Cancer Rate and the Interval Cancer Proportion method.

Results:

Among 441,647 FITs performed for 123,347 individuals, 150 ICs were detected after a negative FIT.

The overall incidence rate of IC was 1.87 × 10,000 person-years (95% CI 1.60 – 2.20), and was higher during the second interval year (OR 1.78; 95% CI 1.28 – 2.47), for proximal locations (OR 3.00; 95% CI 1.92 – 4.68), and among 60- to 71-year-olds (OR 2.37; 95% CI 1.61 – 3.50), with no significant differences regarding sex and stage at diagnosis.

The Proportional Interval Cancer Rate was 13.1%, with an overall sensitivity of 86.9% (95% CI 84.7 – 89.0). Sensitivity was lowest at the first screening round (81.5%; 95% CI 75.6 – 86.2), and increased up to 91.9% (95% CI 83.9 – 96.5) for subsequent rounds. Applying the Interval Cancer Proportion method, sensitivity was 83.9% (95% CI 81.1 – 86.3), and was highest at the first round (89.0%; 95% CI 85.5 – 91.6), ranging between 73% and 83.1% at subsequent rounds.

Conclusions:

A FIT sensitivity for cancer higher than 80% resulted in a low overall incidence of ICs. Due to intrinsic biases, the Proportional Interval Cancer Rate and the Interval Cancer Proportion method generated different trends in FIT sensitivity by screening round. IC incidence rates may provide an accurate picture of the harmful effects associated with false-negative test results.