Review: Daily aspirin reduces short-term risk for cancer and cancer mortality

Question: What are the short-term effects of daily aspirin on cancer incidence and mortality? Review scope: Included studies compared daily aspirin (any dose) with no aspirin. Exclusion criteria were use of other antiplatelet agents, ≤ 90 days of treatment, and studies of secondary prevention or treatment of cancer or colonic polyps. Outcomes included mortality (cancer, nonvascular, vascular, and all-cause) and cancer incidence (excluding nonmelanoma skin cancer). Review methods: MEDLINE, EMBASE/Excerpta Medica, Antithrombotic Trialists' Collaboration (all to May 2011), Cochrane Database of Systematic Reviews, and reference lists of reviews were searched for randomized controlled trials (RCTs). Investigators were contacted for individual patient data on cancer mortality and on incident cancer in primary prevention trials of low-dose aspirin. 51 RCTs of primary and secondary prevention of vascular disease (n = 77 549, mean follow-up 0.5 to 8.2 y) met the selection criteria; individual patient data were available for 6 primary prevention trials of low dose aspirin (n = 35 535). All analyses were intention-to-treat. Main results: Meta-analysis showed that aspirin reduced risk for cancer mortality and nonvascular mortality (Table). Meta-analysis of primary prevention trials showed that aspirin reduced risk for nonvascular mortality but not vascular mortality (Table). Meta-analysis of individual patient data from primary prevention trials of low-dose aspirin (< 300 mg/d) stratified by trial follow-up showed that the effect of aspirin on the incidence of cancer became more apparent with time (P for interaction = 0.04) (Table). Conclusion: Daily aspirin reduces short-term risk for incident cancer and cancer mortality.