Feedback message increased CRC screening participation in non-respondents, while offering sigmoidoscopy decreased it.

This randomized controlled trial enrolled 20,225 individuals aged 54-70 who were previous non-respondents to Florence's colorectal cancer screening program. Participants were randomized to receive either a standard invitation letter (control) or one of five interventions: standard letter plus a feedback message (F), plus a social norm message (MN), plus both messages (F+MN), an offer of sigmoidoscopy (FS) as an alternative to FIT (for ages 58-60 only), or an offer of CT-colonography (CTC) as an alternative to FIT (for ages 58-60 only). The primary outcome was screening participation within 90 days.

Participation was 5.7% in the control group. In the intervention groups, participation was 7.4% (F), 6.7% (MN), 6.6% (F+MN), 2.0% (FS), and 4.1% (CTC). The feedback message alone was associated with increased participation (adjusted odds ratio [aOR]=1.32, 95% CI: 1.10-1.57). In contrast, offering sigmoidoscopy significantly decreased participation compared to the standard FIT invitation (aOR=0.39, 95% CI: 0.27-0.54). Offering CTC resulted in participation similar to the control group among the eligible 58-60-year-old subgroup, and CTC participation was twice that of FS participation.

Safety, tolerability, and adverse event data were not reported. The study has several key limitations. It measured only short-term (90-day) participation and did not assess long-term adherence, cancer detection rates, or patient experience. The findings for offering alternative tests (FS and CTC) are specific to the age subgroup of 58-60 years and may not generalize to other populations or screening contexts.

For practice, this trial provides causal evidence that simple, low-cost behavioral economics interventions like feedback messages can modestly improve CRC screening uptake among previous non-responders in an organized program. However, the results caution against assuming that offering more invasive alternative tests will increase participation; in this setting, it had the opposite effect for sigmoidoscopy. The generalizability of these findings to other healthcare systems and patient populations requires further study.