We know the risk of females developing breast cancer in their lifetime is statistically 1 in 8 and those with a significant family history on the maternal or paternal side have a higher risk. In addition, those who carry a gene mutation such as BRCA1 or BRCA2 have a significantly high risk of developing breast cancer, as well as other cancers. BRCA1 has a markedly increased risk for developing ovarian cancer and BRCA2 increases the risk of getting ovarian, pancreatic, melanoma, and prostate cancer developing in men at a younger age. If a male is carrying a gene mutation, usually the BRCA2 gene mutation, he would only have about a 6% risk of getting breast cancer.
What happens, if anything, for those who were assigned male at birth who are now taking female hormones? Over time, as these levels increase in the blood stream to achieve their desired effects, the individual’s risk can be potentially close to 1 in 8.
Decades of research show that female hormones serve as fuel for more than 70% of breast cancers that occur in either gender. This is why females diagnosed with breast cancer, or who carry a gene mutation and want to reduce their risk biologically (taking medications to suppress female hormone levels) rather than anatomically (mastectomy surgeries), are given selective estrogen receptor modulators (SERMS), or aromatase inhibitors, to accomplish this. Males diagnosed with breast cancer are also given SERMS to prevent recurrence once diagnosed since the majority of male breast cancers are fed by estrogen.
Discussing breast cancer risks with a patient who is being counseled about options for gender reassignment is important. When gathering a family history from a newly diagnosed patient or someone who has been informed that they carry a gene mutation, it is worth discussing family history in a more expansive way. Inquire if there are any male siblings who may be taking female hormones. No further information is really needed than to know this simple question. This could trigger a need for a referral to a genetics counselor for the patient and possibly even other family members depending on the results of such a question.