Associations between aspirin use and the risk of cancers: a meta-analysis of observational studies

Background: Epidemiological studies have clarified the potential associations between regular aspirin use and cancers. However, it remains controversial on whether aspirin use decreases the risk of cancers risks. Therefore, we conducted an updated meta-analysis to assess the associations between aspirin use and cancers. Methods: The PubMed, Embase, and Web of Science databases were systematically searched up to March 2017 to identify relevant studies. Relative risks (RRs) with 95% confidence intervals (CIs) were used to assess the strength of associations. Results: A total of 218 studies with 309 reports were eligible for this meta-analysis. Aspirin use was associated with a significant decrease in the risk of overall cancer (RR = 0.89, 95% CI: 0.87-0.91), and gastric (RR = 0.75, 95% CI: 0.65-0.86), esophageal (RR = 0.75, 95% CI: 0.62-0.89), colorectal (RR = 0.79, 95% CI: 0.74-0.85), pancreatic (RR = 0.80, 95% CI: 0.68-0.93), ovarian (RR = 0.89, 95% CI: 0.83-0.95), endometrial (RR = 0.92, 95% CI: 0.85-0.99), breast (RR = 0.92, 95% CI: 0.88-0.96), and prostate (RR = 0.94, 95% CI: 0.90-0.99) cancers, as well as small intestine neuroendocrine tumors (RR = 0.17, 95% CI: 0.05-0.58). Conclusions: These findings suggest that aspirin use is associated with a reduced risk of gastric, esophageal, colorectal, pancreatic, ovarian, endometrial, breast, and prostate cancers, and small intestine neuroendocrine tumors.