Participation, yield, and interval carcinomas in three rounds of biennial FIT-based colorectal cancer screening

The effectiveness of colorectal cancer screening programs based on the fecal immunochemical test (FIT) is influenced by program adherence during consecutive screening rounds. We aimed to evaluate the participation rate, yield, and interval cancers in a third round of biennial CRC screening using FIT and to compare those with the first and the second screening round.

A total of 3566 average-risk individuals aged 50-75 years were invited to participate in a third round of biennial FIT-based CRC screening. All FIT positives were recommended to undergo colonoscopy. We merged our data with the national cancer registry in the Netherlands to identify all non-screen-detected cancers in our cohort.

Of the invitees, 2142 (60%) returned the FIT in this third screening round, compared to 56% in the second round and 57% in the first round. Overall, 153 of the third-round participants (7.1%) had a positive FIT result, versus 7.9% in the second round and 8.1% in the first round (P=0.05). Of all FIT positives, 123 (80%) underwent colonoscopy. Within this group, 33 persons had advanced neoplasia. The predictive value of FIT positivity for advanced neoplasia was 27% (33/123), compared to 42% in the second round and 54% in the first round - a significant decline (P<0.01).

In an FIT-based screening program, participation rates remained stable over consecutive biennial screening rounds, while the FIT positivity rate and positive predictive value for advanced neoplasia gradually declined. Cancers in non-participants are significantly more advanced in staging than cancers in participants in the first round of screening.