PURPOSE: We examined the association between use of low-dose aspirin and non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs) and endometrial cancer risk in a nationwide case-control study.

METHODS: Cases were all women in Denmark diagnosed with endometrial cancer during 2000-2009. Age-matched female controls were randomly selected by risk-set sampling. Information on NSAID use was collected from the Prescription Registry and classified according to duration and intensity. Conditional logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (CIs), adjusting for potential confounders. Analyses were stratified by endometrial cancer type, and potential effect modification by parity, obesity, and hormone replacement therapy (HRT) use was investigated.

RESULTS: We identified 5,382 endometrial cancer cases and 72,127 controls. Endometrial cancer was not associated with use of low-dose aspirin (OR 0.97, 95 % CI 0.89-1.05) or non-aspirin NSAIDs (OR 0.96, 95 % CI 0.91-1.02) compared with nonuse. The ORs did not vary with increasing duration or intensity of NSAID use or with type of endometrial cancer. Interaction analyses showed reduced endometrial cancer risk associated with low-dose aspirin use among nulliparous women (OR 0.82, 95 % CI 0.70-0.95) and with non-aspirin NSAID use among women having used HRT (OR 0.90, 95 % CI 0.82-0.99).

CONCLUSIONS: We found no association between use of NSAIDs and endometrial cancer risk overall, although there were some indications of risk reductions associated with low-dose aspirin use among nulliparous women and with non-aspirin NSAID use among women having used HRT.