5-α reductase inhibitors, benign prostatic hyperplasia, and risk of male breast cancer

5-α reductase inhibitors (5-ARI) have been suggested to increase the risk of male breast cancer. The aim of this study was to study the risk of breast cancer in men on 5-ARI, in men with benign prostatic hyperplasia (BPH) not on 5-ARI, and in men without BPH.We performed a population-based cohort study in Sweden with data from The Prescribed Drug Register, The Patient Register, and The Cancer Register. Men on 5-ARI, men on α-blockers, or men who...