Long-Term Use of 5α-Reductase Inhibitors and the Risk of Male Breast Cancer

The study, which analyzed data from the United Kingdom Clinical Practice Research Datalink, included 398 male breast cancer cases and 3,930 controls, and found no significant association between the use of 5α-reductase inhibitors (5-ARIs) and the risk of male breast cancer. The adjusted odds ratio for breast cancer in men who had used 5-ARIs was 1.08 (95% CI 0.62-1.87), and no increased risk was observed with longer durations of treatment. The pooled odds ratio from this and a previous study was 1.03 (95% CI 0.52-2.00), suggesting that treatment with 5-ARIs for benign prostatic hyperplasia (BPH) does not significantly increase the risk of breast cancer in older men. Despite potential limitations, the study concluded that there is no significant risk of breast cancer associated with either short-term or long-term use of 5-ARIs.