Inverse association between nonsteroidal anti-inflammatory drugs and prostate cancer.

BACKGROUND: Prostate cancer is considered a major health problem in western countries. Promising results from observational studies on cancer at other sites fuelled the publication of several studies assessing the association between nonsteroidal anti-inflammatory drug (NSAID) use and prostate cancer. However, these studies show conflicting results. METHODS: We conducted a cohort study with a nested case-control analysis to further study the association between NSAIDs and prostate cancer. We used data from the General Practice Research Database in United Kingdom. RESULTS: Aspirin use was associated with a reduced risk of prostate cancer [odds ratio (OR) = 0.70, 95% confidence interval (95% CI) = 0.61-0.79]. We also found that paracetamol use with a treatment duration longer than 1 year was associated with a decreased risk (OR = 0.65, 95% CI = 0.54-0.78). Non-aspirin-NSAID (NA-NSAID) and paracetamol short-term use was associated with a small increased risk whereas long-term users of NA-NSAIDs presented an OR of 0.89 (95% CI = 0.73-1.08). DISCUSSION: Our findings support a protective effect of aspirin and paracetamol against prostate cancer. The transient elevated risk observed among newly started users of NA-NSAIDs and paracetamol is most likely explained by prothopathic bias. We found some suggestion of a reduced risk with long-term use of NA-NSAID.