Recruitment strategies and consent rates in a national prospective colorectal cancer screening cohort: results from year 1 of the Voyage Study.

Objective: To identify the optimal incentive protocol for maximising participation while managing study costs during the Voyage trial.

Design: Prospective cohort (Voyage trial) of colorectal cancer (CRC) incidence and mortality outcomes in individuals screened with multitarget stool DNA (mt-sDNA) served as the population. A subset was randomised to receive postage stamps as a pre-consent incentive, or as a post-consent incentive after completion of the consent and questionnaire. Descriptive statistics from year 1 are reported.

Results: During year 1 of the Voyage trial, a total of 600 258 individuals with mt-sDNA orders received at Exact Sciences Laboratories were randomly selected and invited to participate. Of those, 26 429 (4.4%) opted in, 14 365 of whom (54.3%) consented. The opt-in and consent samples were similar to the target population with respect to sex but differed by geographic residence and age (p<0.001). For the embedded incentive experiment, 2333 were randomised to the pre-incentive arm, while 2342 were randomised to the post-incentive arm. Overall consent rate in the incentive trial was 56.4% (60.9% for the pre-consent incentive arm (1421/2333) vs 52.0% for the post-consent incentive arm (1217/2342), p<0.001). Cost reduction was observed for the pre-consent incentive group, and higher response rates were seen among older versus younger individuals.

Conclusions: Pre-consent incentive option was associated with a higher participation rate and lower costs and was used for the remainder of study recruitment. CRC incidence and mortality vary with age; thus, adjusting for differential participation by age and region will be important in analyses of Voyage data.

Trial registration number: NCT04124406.