Effects of daily aspirin on cancer incidence and mortality in the elderly Japanese

Essentials The effects of aspirin on cancer incidence and mortality in the elderly Japanese are not clear. We analyzed cancer incidence and mortality in the Japanese Primary Prevention Project (JPPP). Low-dose aspirin for 5 years did not reduce cancer incidence or cancer mortality in the JPPP. Cancers might be diagnosed earlier in the aspirin group. Background: Long-term follow-up of studies to investigate preventive effects of aspirin on arterial thrombosis indicate that aspirin reduces the incidence and mortality of some cancers in Western populations. Objectives: To explore the effects of aspirin on cancer incidence and mortality in the elderly Japanese. Patients/Methods: Patients aged 60 to 85 years, presenting with hypertension, dyslipidemia, or diabetes mellitus (n = 14 601, 7297 in the aspirin group and 7304 in the no-aspirin group) participated the Japanese Primary Prevention Project (JPPP), a multicenter, open-label, randomized, parallel-group trial. A subanalysis of JPPP was performed to analyze the incidence of newly diagnosed cancer and death related to cancer. Results: The cumulative incidence of newly diagnosed cancer was 5.60% (4.65-6.64%) in the aspirin group and 4.14% (3.67-4.66%) in the no-aspirin group. The hazard ratio for newly diagnosed cancer was 1.24 (1.06-1.46), and the cancer incidence was significantly higher in the aspirin group. The cumulative cancer mortality was 1.96% (1.65-2.31%) in the aspirin group and 1.87% (1.56-2.22%) in the no-aspirin group, with no statistically significant difference. The Fine and Gray model suggested that the difference in the incidence of newly diagnosed cancer between the two groups decreased year by year. Conclusions: Low-dose aspirin use did not reduce the cancer incidence or cancer mortality during a 5-year-average study period in the elderly Japanese. The cancer incidence in the aspirin group might decrease, however, to less than that in the no-aspirin group after the study period. Aspirin use might have led to earlier cancer diagnosis in our study.