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Testosterone therapy and risk of breast cancer development: a systematic review.

PURPOSE OF REVIEW
We aim to conduct a systematic review of the literature, document all reported cases of breast cancer development in cis men and female-to-male (FtM) transgender men undergoing testosterone replacement therapy (TRT), and determine if testosterone poses a substantial risk of breast cancer development and recurrence.


RECENT FINDINGS
A systematic search through December 2019 was performed. Out of 1890, 15 studies were eligible for inclusion in the final analyses. In total, 22 patients have developed breast cancer while on testosterone treatment. Four cases were cis men, whereas 18 cases were FtM. Age ranged from 18 to 61 years. Testosterone treatment duration ranged from 5 weeks up to 25 years.


SUMMARY
There is a relatively higher incidence of BCa in FtM on CSH therapy compared with cis men on TRT. Because of the small sample size of reported cases, we cannot delineate the exact relationship between testosterone therapy and BCa development. Additionally, we have limited data to suggest that TRT should or should not be contraindicated in cis men and FtM with a prior history of breast cancer.