Safety of 5α-Reductase Inhibitors and Spironolactone in Breast Cancer Patients Receiving Endocrine Therapies

The review, which included 47 studies from January 1978 through April 2018, aimed to evaluate the safety of 5α-reductase inhibitors and spironolactone in breast cancer patients on endocrine therapies. It found that 5α-reductase inhibitors did not consistently affect serum estrogen levels in 284 female patients, with 34% showing increased levels, 5.3% decreased, and 57% no change. Similarly, spironolactone did not consistently affect estrogen levels in 95 female patients, with 26% increased, 6.3% decreased, and 67% no change. Additionally, no increased breast cancer risk was observed in 49,298 patients taking spironolactone across three studies. The review concluded that spironolactone does not significantly increase breast cancer risk and could be considered for further research on alopecia and hirsutism in breast cancer patients. However, the efficacy of finasteride for treating female androgenetic alopecia remains controversial, and it is not recommended for women with endocrine therapy-induced alopecia until more is known about its long-term implications. Spironolactone may be a relatively safe systemic treatment option for managing EIA in female breast cancer patients and survivors.