The risk of breast cancer is a concern for trans women transitioning using estrogen and anti-androgens: they experience the growth of substantial breast tissue just as cis women do, and the use of estrogen could promote the growth of any estrogen-sensitive breast cancers. Researchers have found that breast cancer in trans women is not overly common, and that breast cancer occurs at roughly the same rates in trans women as in cis women (Brown & Jones, 2015).
However, the potential for developing breast cancer is an especially serious issue for trans women with mutations in the BRCA1 or BRCA2 genes. Similar to cis women, trans women with these mutations are at a much higher risk for developing breast cancer. The question of how such patients should be treated in terms of hormone therapy – does HRT pose unacceptable risks? how should the risk of breast cancer be managed? – has been examined in several publications.
Colebunders et al. (2014) describe their approach in the treatment of a trans woman who carried a BRCA1 mutation. While she continued receiving estrogen and did not have a prophylactic mastectomy, the authors note that preventive mastectomy should be considered:
Bilateral prophylactic mastectomy has been shown to reduce the risk of breast cancer in biological women with BRCA1 mutations. The risk of developing breast cancer in trans-women with BRCA1 mutations taking cross-sex hormones is unknown. However, the possibility of preventive mastectomy and primary reconstruction with either autologous tissue or prosthesis should be discussed with these patients.
They further add that “transgender persons should be encouraged to participate in relevant cancer screening protocols, which for breast cancer screening are the same as for cisgender women.” Finally, trans women seeking HRT should be routinely screened for a family history of certain cancers:
The consequences of hormonal therapy in such a person are unknown but are likely to increase the risk to develop breast cancer. Therefore, similar individuals should be carefully monitored and if cancers develop, this should be reported. Psychological counselling about bilateral prophylactic mastectomy and consecutively primary reconstruction with either autologous tissue or prosthesis should be offered in patients with a BRCA1 mutation.
This case clearly points to the importance of routine investigation of family history. Screening for BRCA mutations should be considered in patients with multiple breast and/or ovarian cancers within their family (often diagnosed at an early age), or two or more primary breast and/or ovarian cancers in a single family member and/or cases of male breast cancer within their family.
More recently, Wolf-Gould, Riley, & Carswell (2018) described the case of a 14-year-old transfeminine adolescent with a BRCA1 mutation, who was taking puberty blockers and wanted to begin estrogen treatment:
The physician received permission from the family to discuss their case with colleagues and connected with two other physicians experienced in providing hormones for transgender patients, who were also struggling with the care of BRCA1+ transgender youth. The three physicians outlined options and risks for care, including (1) stopping GnRH analogues and allowing the youth to experience puberty in their assigned gender (unacceptable risks of gender dysphoria), (2) continuing GnRH analogues indefinitely, with surgical gender transition (unacceptable risks of osteoporosis), (3) watchful waiting on GnRH analogues until the youth reached the age of consent (risk of delay in puberty and uncertain utility), and (4) proceeding with induction of feminizing hormones with recommendations for appropriate cancer screening (question increased risk of cancers). All physicians agreed that the need to respect the youth’s and parent’s autonomy to decide on treatment was essential.
The family and physician completed the process of informed consent, which included cancer screening recommendations. The physician agreed to prescribe estradiol for induction of puberty as soon as the family and therapist felt that all were ready.
A genetics counselor recommended close monitoring for breast cancer after starting HRT:
The genetics counselor acknowledged that there were no data regarding the risks of cancers in male to female transgender people, but felt it was likely that estrogen therapy would increase the risk of breast cancer. She recommended screening breast magnetic resonance imaging on a yearly basis starting at age 25, annual mammograms starting at age 30, consideration of a prophylactic mastectomy after age 20, and consultation with an oncologist before proceeding with hormone therapy.
While trans women with BRCA mutations likely face a highly elevated risk of breast cancer, the existing literature indicates that clinicians can nevertheless provide HRT to these patients, and that those who do choose to start HRT should receive frequent screening and be aware of the option of mastectomy and reconstruction. ■
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