Aspirin has been associated to a reduced risk of colorectal and other selected digestive tract cancers, but the evidence other neoplasms is still controversial. In order to provide an up‐to‐date quantification of the role of aspirin on lung, breast, endometrium, ovary, prostate, bladder, and kidney cancer, we conducted a systematic review and meta‐analysis of all observational studies published up to March 2019.
We estimated pooled relative risk (RR) of cancer or cancer death for regular aspirin use versus non‐use using random‐effects models, and, whenever possible, we investigated dose‐ and duration‐risk relations. A total of 148 studies were considered. Regular aspirin use was associated to a reduced risk of lung (RR=0.88, 95% confidence interval, CI=0.79‐0.98), breast (RR=0.90, 95% CI=0.85‐0.95), endometrial (RR=0.91, 95% CI=0.84‐0.98), ovarian (RR=0.91, 95% CI=0.85‐0.97), and prostate (RR=0.93, 95% CI=0.89‐0.96) cancer.
However, for most neoplasms nonsignificant risk reductions were reported in cohort and nested case‐control studies, and there was between‐study heterogeneity. No association was reported for bladder and kidney cancer. No duration‐risk relations for most neoplasms were observed, except for an inverse duration‐risk relation for prostate cancer.
The present meta‐analysis confirms the absence of appreciable effect of regular aspirin use on cancers of the bladder and kidney, and quantifies small and heterogeneous inverse associations for other cancers considered.