Benefits and harms of aspirin to reduce colorectal cancer risk: a cross-sectional study of methods to communicate risk in primary care.

Background: New Australian guidelines recommend that GPs actively consider prescribing low-dose aspirin to patients aged 50-70 years to reduce their risk of developing colorectal cancer (CRC). Patients and GPs need to understand the relative benefits and harms to support informed decision making.

Aim: To develop and examine different methods to communicate the benefits and harms of taking aspirin for CRC prevention.

Design And Setting: A cross-sectional, vignette study with patients aged 50-70 years consecutively recruited from general practices in Melbourne, Australia, between July and August 2018.

Method: Summary estimates from meta-analyses of the effects of aspirin on the incidence of CRC, cardiovascular disease, gastrointestinal bleeding, and incidence rates in the Australian population to estimate outcomes in a hypothetical population of 10 000 people aged 50-70 years. These estimates were presented using four different risk communication formats. Participants were shown these different formats and asked if they would take aspirin to prevent CRC.

Results: A total of 313 participants were recruited (95.1% recruitment rate), of whom 304 completed the study. Most participants (71.7-75.3%) reported they would take aspirin irrespective of risk format presented. Bar charts (odds ratio [OR] 1.20, 95% confidence intervals [CI] = 1.01 to 1.44) and expected frequency trees (OR 1.18, 95% CI = 0.99 to 1.41) were more strongly associated with the intentions to take aspirin compared with icon arrays. Bar charts were most preferred for presenting risk information.

Conclusion: A large proportion of participants in this study intended to take aspirin to reduce their CRC risk regardless of risk communication format. Bar charts and expected frequency trees were the preferred methods to present the benefits and harms of taking aspirin to prevent CRC.