Involvement of previous non-participants cannot fully compensate for lower participation in a second round of FIT-screening

Introduction: The effectiveness of colorectal cancer (CRC) screening programs depends on repeated participation. Little is known on later rounds in programs that use the fecal immunochemical test (FIT), in particular whether previous participants are likely to participate again, and if non-participants persist in declining. We compared overall participation in a second round to that in a first round, and evaluated differences in participation rates based on previous response. Methods: Asymptomatic persons aged 50–74 years were invited to a second round of a FIT-based CRC screening pilot. We assessed the participation rate overall and within second round subgroups of previous participants, previous non-participants, and first time invitees. We also assessed whether participation rates were similar for males and females and for age groups. Results: In the first screening round, 2871 of 5309 invitees returned the FIT (participation rate of 57%). This was higher than in the second in which 3187 of 5925 participated (54%; p = 0.0008). Second round participation rate was 85% (2034/2385) among previous participants, 18% (325/1826) among previous non-participants and 48% (828/1714) among first time invitees (p < .0001). Overall, males and persons aged under 55 were less likely to participate. Conclusions: Participation in a second round of FIT-screening was significantly lower than in the first round, largely due to a drop in participation in first round participants, and a relatively low response among first time invitees. This loss of uptake was partially compensated by a willingness to be screened in previous non-participants.