TLDR Finasteride use may increase the risk of male breast cancer.
The study analyzed the link between finasteride use and male breast cancer (MBC) in a cohort from Denmark, Finland, Norway, and Sweden, with 1,365,088 person-years of follow-up. It found a 44% increased risk of MBC among finasteride users, with an incidence rate ratio (IRR) of 1.44. The risk was even higher, with an IRR of 1.60, when excluding users from Norway and Sweden with short follow-up times. The greatest risk was seen in men with medium duration of use and those who started finasteride 1-3 years before diagnosis. The study noted potential biases and recommended further research due to limitations such as possible ascertainment bias and the inability to adjust for all confounding factors. Despite these limitations, the study suggested an increased risk of MBC with finasteride use, especially in Denmark and Finland.
28 citations,
August 2014 in “Cancer Causes & Control” Taking 5α-reductase inhibitors does not significantly increase the risk of breast cancer in men.
32 citations,
May 2013 in “The Journal of Urology” Using finasteride or dutasteride does not increase the risk of male breast cancer.
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December 2003 in “The New England Journal of Medicine” Combination therapy of doxazosin and finasteride safely and effectively reduces benign prostatic hyperplasia progression risk.
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February 1998 in “The New England Journal of Medicine” Finasteride reduces urinary issues and surgery need in men with enlarged prostates by over 50%.
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March 2019 in “Cancer Epidemiology, Biomarkers & Prevention” Finasteride use is not clearly linked to an increased risk of male breast cancer.
1 citations,
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December 2013 in “Urological Science” A man developed male breast cancer after four years of finasteride treatment for an enlarged prostate.
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October 2018 in “International Braz J Urol” Taking 5-alpha reductase inhibitors does not increase the risk of breast cancer in men.