e16013 Background: 5-alpha reductase inhibitors (5ARIs), finasteride and dutasteride, are one of the most popular classes of medications used by older men. The drugs are mainly used for the treatment of benign prostatic hyperplasia (BPH). There have been 50 cases of breast cancer potentially linked to both finasteride and dutasteride reported to the FDA. However, to date, no epidemiologic study has examined this potential link. Methods: We used the LifeLink database (IMS, USA) as the main source of data for this study. The database captures information on approximately 70 million US residents who are enrolled in a private healthcare plan. The database captures information on prescription drugs, hospitalizations, physician visits and demographics. Breast cancer cases were defined as those with a diagnosis (ICD-9-CM 175.X) on two days and either a procedural code (CPT-4) for a mastectomy or a lumpectomy/partial mastectomy with evidence of follow-up treatment (radiation/chemotherapy). The index date was deemed the first diagnostic or procedural code for breast cancer. This definition has been found to have a 93% positive predictive value for incident breast cancer. For each case, twenty controls were selected from the database using risk set sampling and matched on age within 5 years, date of diagnosis within six weeks and follow up time prior to the index date. We used logistic regression to compute adjusted rate ratios. The model was adjusted for the following covariates: age, calendar year, alcoholism, gynecomastia, Klinefelter’s disease, liver damage, obesity, oral estrogen, orchiectomy, and prior radiation. Results: There were 429 male breast cancer cases and matched them to 13,240 controls. 341 (79.5%) met our primary ascertainment, while 88 (20.5%) additional cases met our secondary criteria. We found no increased risk with male breast cancer and use of 1 year (RR=0.70, [95% CI0.34-1.45]) or 3 years of 5-ARIs therapy (RR=0.71, [95% CI:0.25-1.98]). Conclusions: We found no harmful association between sue of 5-ARIs and risk of male breast cancer. Future studies are needed to refute or confirm these findings.
5-alpha Reductase inhibitors and risk of male breast cancer: a systematic review and meta-analysis