2015 Study Conclusions
Breast cancer in transgender patients is rarely reported, and when it is, it is often in association with the receipt of CSH and mentioned as a potential adverse effect of cross-sex hormones (CSH). This report expands the number of reported cases from 15 (10 in male-to-female (MtF), 5 in female-to-male (FtM)) to 25 (13 in MtF, 12 in FtM) in the English literature. Maglione and colleagues, reporting on two cases, concluded that breast cancer occurs in MtF transsexuals who receive “high doses of exogenous estrogens,” which results in an increased risk of breast cancer. Researchers using large cohorts of transgender/transsexual patients followed prospectively have not detected an increased incidence relative to the general population. However, breast cancer can occur, in theory, in the absence of known CSH treatment, in persons with a diagnosis of gender dysphoria, or in a way that is associated with, but unrelated, to gender dysphoria. Given that it is well known that patients who seek CSH treatment from medical sources may also obtain CSH from nonmedical sources in unknown quantities, it is difficult to conduct dose–response studies linking CSH dose/exposure to breast cancer outcomes. It should be noted that this case series derives only from transgender veterans who were identified based on a clinical, psychiatric diagnosis. It is likely that there are many more veterans who self-identify as transgender who did not receive one of the four qualifying psychiatric diagnoses. The number of breast cancer cases in those veterans cannot be determined.
These 10 case reports do not attempt to link CSH to outcome, especially given the fact that provision of CSH treatment was not openly available to gender dysphoric veterans until 2011. Therefore, the VHA EHR for these cases include only information about CSH provided by VHA clinicians. All three birth sex male cases in this series presented with late-stage disease and died from metastatic cancer, whereas the birth sex female patients with gender dysphoria had all been treated and, in all but one case, had survived at least 2 and as long as 25 years after initial diagnosis or at the end of the observation period.
Although apparently rare, breast cancer does occur in transgender people of both birth sexes, and screening methods generally in place for nontransgender persons should be sensitively discussed and applied by clinicians providing transgender healthcare, whether or not CSH medications are utilized. In addition, family histories of breast cancer should be elicited from all transgender persons as part of their routine medical care.