Abstract A69: The association between NSAID use and colorectal cancer mortality: Results from the Women's Health Initiative

Abstract

Abstract Introduction: Observational and experimental evidence demonstrate that non-steroidal anti-inflammatory drug (NSAID) use reduces the incidence and recurrence of colorectal neoplasia. Consistent with such observations, recent studies have also suggested an inverse association between NSAID use, particularly long-term use, and colorectal cancer (CRC) mortality. We examined the association between aspirin and non-aspirin NSAID use and colorectal mortality among post-menopausal women enrolled in the clinical trial and observational study arms of the Women's Health Initiative (WHI). Methods: We investigated the effect of NSAID use on colorectal cancer mortality among 160,143 women enrolled in the WHI with available follow up data who did not report a prior history of colorectal cancer at the time of study entry. Women provided details on aspirin and non-aspirin NSAID use at both study baseline and three years after enrollment. Reported cases of colorectal cancers were locally confirmed based on medical records and also centrally adjudicated. Cause of death was determined according to centralized medical record and death certificate review; routine linkages were made to National Death Index files to ensure the completeness of vital status information. There were 2,119 confirmed cases of colorectal cancer and 492 deaths among WHI participants where the listed cause of death was colorectal cancer. Cox proportional hazards regression was used to examine the relationship between NSAID use (at study baseline and at year 3 of study follow-up) and colorectal cancer mortality and to estimate hazard ratios and 95% confidence intervals. We conducted a sensitivity analysis that excluded women who developed colorectal cancer within the first three years following study enrollment (n=180) in order to restrict the study question to examining the role of NSAID use prior to diagnosis on colorectal cancer mortality. Results: Reported use of NSAIDs at study baseline, including aspirin, ibuprofen, and prescription NSAIDs, was not associated with colorectal cancer mortality (HR: 0.93; 95% CI 0.76–1.14). However, among women who lived to year 3 after study enrollment (n=156,440; 98% of participants), those who reported use of NSAIDs at both baseline and year 3 experienced reductions in colorectal cancer mortality of approximately 30% (HR: 0.72; 95% CI 0.54–0.95) compared to women who did not report use at both time points. Results from the sensitivity analysis demonstrated that prolonged pre-diagnostic NSAID use (use at both baseline and year 3) was significantly associated with reduced colorectal cancer mortality (HR: 0.70; 95% CI 0.52–0.93). Conclusion: Our results suggest that use of NSAIDs is associated with lower colorectal cancer mortality among post-menopausal women, particularly in women who use these medications for longer periods of time prior to diagnosis. This association may reflect an effect of NSAID use in decreasing the incidence of new tumors and/or an effect in lowering rates of disease progression. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A69.