A Population-Based Nested Case-Control Study in Taiwan: Use of 5α-Reductase Inhibitors Did Not Decrease Prostate Cancer Risk in Patients with Benign Prostate Hyperplasia

Background. 5 alpha-Reductase inhibitors (5ARIs) are commonly used to treat benign prostate hyperplasia (BPH) by blocking the conversion of testosterone into the more potent dihydrotestosterone. This study explored a possible association between the use of the 5ARIs finasteride and dutasteride and the subsequent risk of prostate cancer or other cancers. Methods. We analyzed data from the Taiwanese National Health Insurance system. In a BPH cohort, we identified 1,489 patients with cancer and included them in our study group. For the control group, 3 patients without cancer were frequency matched with each BPH case for age, BPH diagnosis year, index year, and month. Information regarding past 5ARI use was obtained from the Taiwanese National Health Insurance Research Database (NHIRD). Multivariate logistic regression analysis was conducted, and odds ratio (OR) and 95% confidence interval (CI) were estimated. Results. Finasteride use marginally increased the incidence of prostate and overall cancer at a level of statistical significance (prostate cancer: OR = 1.90; 95% CI: 1.00-3.59; overall cancer: OR = 1.51; 95% CI: 1.00-2.28). Dutasteride use significantly increased kidney cancer risk (OR = 9.68, 95% CI: 1.17-80.0). Dosage analysis showed that lower doses of finasteride were associated with higher overall and prostate cancer risks. The major limitation is the lack of important data in the NHIRD, such as prostate cancer histologic grades, smoking habits, alcohol consumption, body mass index, socioeconomic status, and family history of cancer. Conclusions. This population-based nested case-control study suggested that finasteride use may increase prostate and overall cancer risks for patients with BPH. The effects were more prominent for patients using lower doses of finasteride. The Oncologist 2012;17:986-991