A factorial randomised trial investigating factors influencing general practitioners’ willingness to prescribe aspirin for cancer preventive therapy in Lynch syndrome: a registered report

We investigated the optimal type and level of information to communicate with GPs to increase willingness to prescribe aspirin for colorectal cancer prevention. We recruited GPs in England and Wales (n=672) to an online survey with a 2 by 3 factorial design. GPs were randomised to one of eight vignettes describing a hypothetical patient with Lynch syndrome recommended to take aspirin by a clinical geneticist. Across the vignettes, we manipulated the presence or absence of three types of information: 1) existence of NICE guidance; 2) results from the CAPP2 trial; 3) information comparing risks/benefits of aspirin. We estimated the main effects and all interactions on the primary (willingness to prescribe) and secondary outcomes (comfort discussing aspirin).