Background: COX-2 overexpression may contribute to colorectal cancer occurrence. Aspirin and nonsteroidal antiinflammatory drugs (NSAIDs) can reduce colorectal cancer recurrence, but the efficacy of primary prevention in Asian populations is still elusive. Thus, we examined the primary preventive efficacy of aspirin and NSAIDs on colorectal cancer incidence in Taiwan. Methods: A nested case-control study was conducted using the National Health Insurance Research Database (NHIRD) in Taiwan. We identified patients with diagnosis of colorectal cancer from 2005 to 2013 in the Registry of Catastrophic Illness Patient Database. We selected patients without colorectal cancer from the Longitudinal Health Insurance Database as the controls and matched them with cases. NSAID exposure was defined as at least two prescriptions 13 to 48 months prior to the index date. Conditional logistic regression models were performed to evaluate the association between NSAID use and colorectal cancer. Results: A total of 65,208 colorectal cancer cases and 65,208 matched controls were identified. Patients with aspirin use had a lower risk of colorectal cancer compared with nonusers [adjusted OR (AOR) = 0.94, 95% confidence interval (CI) = 0.90-0.99]. NSAID use was associated with lower incidence of colorectal cancer (AOR = 0.96; 95% CI = 0.92-1.00). When examining colon or rectal cancer, similar decreased risks were observed. Patients taking more cumulative days of NSAIDs use tended to experience a more protective effect on colorectal cancer, but no dose-response effects were noted. Conclusions: Aspirin and NSAIDs were associated with a reduced risk of colorectal cancer development among a study cohort in an Asian population. Impact: This study provided a possible chemoprevention for colorectal cancer in an Asian population.
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