Effect of Aspirin on Cancer Chemoprevention in Japanese Patients With Type 2 Diabetes: 10-Year Observational Follow-up of a Randomized Controlled Trial

OBJECTIVE This study analyzed the efficacy of low-dose aspirin in cancer chemoprevention in patients with diabetes. RESEARCH DESIGN AND METHODS This study was a posttrial follow-up of the Japanese Primary Prevention of Atherosclerosis with Aspirin for Diabetes (JPAD) trial. Participants in the JPAD trial (2,536 Japanese patients with type 2 diabetes and without preexisting cardiovascular disease) were randomly allocated to receive aspirin (81 or 100 mg daily) or no aspirin. After that trial ended in 2008, we followed up with the participants until 2015, with no attempt to change the previously assigned therapy. The primary end point was total cancer incidence. We investigated the effect of low-dose aspirin on cancer incidence. RESULTS During the median follow-up period of 10.7 years, a total of 318 cancers occurred. The cancer incidence was not significantly different between the aspirin and no-aspirin groups (log-rank, P = 0.4; hazard ratio [HR], 0.92; 95% CI, 0.73-1.14; P = 0.4). In subgroup analyses, aspirin did not affect cancer incidence in men, women, or participants aged 65 years. However, it decreased cancer incidence in participants aged <65 years (log-rank, P = 0.05; HR, 0.67; 95% CI, 0.44-0.99; P = 0.048). After adjusting for sex, hemoglobin A(1c), smoking status, and administration of metformin and statins, aspirin significantly reduced cancer incidence in participants aged <65 years (adjusted HR, 0.66; 95% CI, 0.43-0.99; P = 0.04). CONCLUSIONS Low-dose aspirin did not reduce cancer incidence in Japanese patients with type 2 diabetes.