Current Research on Breast Cancer in Transgender Men and Women

All people, regardless of their sex assigned at birth, have breast tissue, meaning everyone has the potential to develop breast cancer. However, the issue of breast cancer among the trans community is understudied, but is somewhat unique and deserving of attention.

As a primer, transgender men, or trans men, are men who were assigned the female sex at birth and trans women are women who were assigned the male sex at birth. Cisgender refers to a person “whose gender identity corresponds with the sex the person had or was identified as having at birth.”

Although there are variations in regards to how people transition from one gender to another, often this process includes medical interventions, such as surgeries and hormones. According to a longitudinal Dutch study, while transgender men who get mastectomies and take male hormone medications have a lower chance of getting breast cancer, transgender women may have a greater chance of breast cancer if they take female hormone medicines.

Two thousand, two hundred and sixty transgender women and 1,229 adult transgender men were followed in the retrospective cohort study from 1972 to January 2016 to investigate the incidence rate and characteristics of breast cancer in transgender people versus the general population in the Netherlands. These rates were compared to rates in the cisgendered community, in which “the lifetime risk in the general female population is 12% and in the general male population is 0.1%.”[1]

The use of gender affirming hormones, such as anti-androgen and estrogen for trans women and testosterone for trans men, is important to track for a study of breast cancer in the trans population because those interventions induce changes in breast tissue. The Dutch study acknowledges this and includes the use of the hormones in their criteria. People were excluded from the study if they received reversed hormone treatment, had an unknown start date of hormone treatment, were younger than 18 years old at the time of the study, alternated between testosterone and estrogen, and/or had their last doctor’s visit focused on transitioning before 1991.

The study found an increased risk of breast cancer in trans women compared with cisgender men and a lower risk of breast cancer in trans men when compared to cisgender women.[1] There were 17 cases of invasive breast cancer among the 2,260 trans women in the study. The median duration of hormone treatment in the population was 18 years and the median age of diagnosis was 50 years old. Most of their tumors were of ductal origin, meaning the tumors began in the “milk ducts, which are the ‘pipes’ that carry milk from the milk-producing lobules to the nipple.”

In comparison, among the 1,229 trans men, there were 4 cases of invasive breast cancer. Participants were a median age of 47 and were using hormone treatments for a median of 15 years. Three of the four tumors were ductal origin.

In studying transgender men and women, there were some informative trends about the impact of hormone treatment on incidence of breast cancer. For example, “in transgender women, the risk of breast cancer increased during a relatively short duration of hormone treatment [18 years] and the characteristics of the breast cancer resembled a more female pattern.”[1] Perhaps the different molecular development in breast cancer cases between the sexes influenced that finding.

The Dutch study emphasizes that “hormone treatment alters the risk of breast cancer in transgender people compared with initial risk based on their birth assigned sex.”[1] For example, breast cancer diagnosis occurred at a younger age in the transgender population in comparison to cisgender women. Still, in both trans men and women, the risk of breast cancer was lower than in cisgender women. Therefore, the study concludes that transgender people are able to use the same breast cancer screening guidelines as cisgender individuals use because the absolute overall risk of breast cancer in transgender people remains low.

So, what are those screening techniques?

The University of California, San Francisco has published guidelines for screening for breast cancer in transgender individuals while citing that a reduced risk of breast cancer among the population is due to “potentially less lifetime overall or cyclical exposure to estrogen and in some cases the absence of or minimal exposure to progesterone.”[2] Their recommendations align with those from the Dutch study even though they were actually based on a retrospective cohort study of 1,263 transgender women who were receiving care at large urban community health centers in the United States. That particular study found that “transgender individuals between ages 50-74, and with a history of at least 5 years of hormone therapy were significantly less likely than non-transgender individuals to have a mammogram per guidelines.”[2]

Based on that finding and the fact that there is a likely lower incidence in transgender women, the University of California, San Francisco recommends that screening mammography for trans women should not begin before the age of 50. Additionally, screening is ineffective if the patient does not have a minimum of five years of hormone treatment. Therefore, the frequency of screening should be every two years once the patient turns 50 and has received 5-10 years of hormone use.

Given these recommendations, some hospitals do note that there is a risk of too much breast cancer screening for trans women; the age and frequency of screening is important to take note of in a patient. The guidelines focused mainly on trans women and stated that “transgender men who have undergone bilateral mastectomy have an unknown risk of breast cancer associated with residual breast tissue.”[2]

As society evolves to recognize the rights and lives of transgender people, it is hoped more research will be done to better understand the health of the trans community. The information above gives insight into breast cancer risk for this population and highlights the screening guidelines specifically for trans women. While all of the participants in the study came from clinics, the question still remains how easy is it for them to be granted breast cancer screening and whether or not their changed gender creates a stigma that impacts the screening process. The Dutch study’s findings are only impactful if they can be applied to the lives of trans men and women without obstacles.

References

1. de Blok Christel J M, Wiepjes Chantal M, Nota Nienke M, van Engelen Klaartje, Adank Muriel A, Dreijerink Koen M A et al. Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the Netherlands BMJ 2019; 365 :l1652
2. Deutsch, M. B. (2016). Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People (2nd ed.). University of California, San Fransisco .