Low-dose Aspirin and Cancer Mortality

Low-dose aspirin is a common strategy for preventing cardiovascular disease and associated mortality. A recent individual patient data meta-analysis of 8 trials of low- and high-dose aspirin, with long-term follow-up, found important reductions in cancer mortality. The study was aimed at determining whether cancer mortality also is reduced by low-dose aspirin in the shorter term.

Researchers conducted a comprehensive search of 10 electronic databases up to December 2011, then conducted a meta-analysis using data from all randomized clinical trials evaluating low-dose (75-325 mg) daily aspirin, and extracted data on non-cardiovascular disease mortality and cancer mortality. They then pooled the studies using a random-effects model and conducted a meta-regression and finally supplemented this with a cumulative meta-analysis and trial sequential monitoring analysis.

The analysis, confirmed the findings of a previous individual patient data meta-analysis that aspirin exhibits large cancer mortality protection. Additional knowledge based on this analysis includes the protective status of exclusively low-dose aspirin, the use of all published data, and the confirmation that aspirin protective elements seem to begin in the short term (∼4 years). These findings highlight the important role of aspirin in cancer protection and should be clinically useful for counseling both low- and high-risk patients with cardiovascular disease on the use of aspirin. Because any aspirin use is associated with increased risk of both gastrointestinal and nongastrointestinal bleeding, including cerebral bleeds, clinicians should be aware that the benefits of aspirin use must be balanced with bleeding risks.

The results showed twenty-three randomized studies reported on nonvascular death. There were 944 nonvascular deaths of 41,398 (2.28%) patients receiving low-dose aspirin and 1074 nonvascular deaths of 41,470 (2.58%) patients not receiving aspirin therapy. The relative risk of nonvascular death was 0.88 (95% confidence interval [CI], 0.81-0.96, I² = 0%). Eleven trials included data evaluating cancer mortality involving 16,066 patients. There were 162 of 7998 (2.02%) and 210 of 8068 (2.60%) cancer deaths among low-dose aspirin users versus non-aspirin users, respectively, reported over an average follow-up of 2.8 years. The relative risk of cancer mortality was 0.77 (95% CI, 0.63-0.95, I² = 0%). Studies demonstrated a significant treatment effect after approximately 4 years of follow-up. The optimal information size analysis showed that a sufficient number of patients had been randomized to provide convincing evidence of a preventive role of low-dose aspirin in nonvascular deaths.

From the results it was concluded that, nonvascular deaths, including cancer deaths, are reduced with low-dose aspirin.

The American Journal of Medicine Volume 125, Issue 6 , Pages 560-567, June 2012