Aspirin has been associated with a reduced risk of colorectal cancer. With specific reference to urological cancers, a protective role for aspirin has been suggested for prostate cancer, but data for cancers of the bladder and kidney have been limited and inconsistent. Epidemiological evidence suggests that prostate cancer risk is reduced by 10% in regular aspirin users, with similar risk reductions reported in both case-control and cohort studies, and for both slow-growing and aggressive cancers. However, risk estimates were significantly heterogeneous and there was no relationship between risk reduction and frequency, dose or duration of use. Thus, inference for causality and public health implications remain far from conclusive. Although a few case-control studies have reported a favorable effect of aspirin on bladder cancer, most investigations did not find any meaningful association. A modest nonsignificant increased risk was reported for kidney cancer. Such excess risk, however, might be due to exposure to phenacetin-containing analgesics, which have been reported to increase renal cell cancer risk.
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