Feminizing Hormones Linked to Higher Breast Cancer Risk in Trans Women, but Risk Still Lower Than Average Woman’s

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Transgender women — people who are born with male genitalia but who identify with the female gender — who take feminizing hormone therapy have a higher risk of breast cancer compared to the average man, according to a Dutch study. Still, this increase in risk is small and is not as high as the average woman’s breast cancer risk.

The results also found that transgender men — people who are born with female genitalia but who identify with the male gender — who take masculine hormones have a lower risk of breast cancer than the average woman.

The research was published online on May 14, 2019, by the journal BMJ. Read “Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the Netherlands.”

Study background

Menopausal symptoms such as hot flashes and night sweats can dramatically reduce quality of life for some women. Some women use hormone replacement therapy (HRT) to ease these symptoms. Still, past research has shown that HRT can increase the risk of breast cancer in postmenopausal women.

Transgender people have a sense of personal identity and gender that doesn’t correspond to the sex assigned to them at birth. Some transgender people choose to take hormones to make them look more like the gender with which they identify.

Cisgender is the term for people who identify as the gender that matches the sex they were assigned at birth.

Because HRT has been linked to increased breast cancer risk, the researchers wanted to know if gender hormone therapy affected breast cancer risk in transgender women and transgender men.

How the study was done

The study included 2,260 transgender women and 1,229 transgender men who were taking hormones and being seen at a specialty clinic in Amsterdam between 1972 and 2016.

On average, transgender women were 31 years old when they started hormone treatment and transgender men were 23 years old.

Transgender women took hormones for an average of 13 years, and transgender men took hormones for an average of 8 years.

During the study, 15 cases of invasive breast cancer were diagnosed in the transgender women at an average age of 50 and after an average of 18 years of hormone treatment.

This rate was higher than the rate of breast cancer in the general cisgender male population, but lower than the rate of breast cancer in the general cisgender female population.

Four cases of invasive breast cancer were diagnosed in the transgender men at an average age of 47 and after an average of 15 years of hormone treatment.

This rate was lower than the rate of breast cancer in the general cisgender female population.

“This study found an increased risk of breast cancer in trans women in the Netherlands compared with Dutch cisgender men,” the researchers wrote. “In both trans women and trans men, the risk of breast cancer was lower than in Dutch cisgender women. This suggests that hormone treatment alters the risk of breast cancer in transgender people compared with initial risk based on their birth assigned sex.

“Current recommendations suggest that trans women and trans men who have not undergone mastectomy should be biennially screened with mammography from the age of 50 years and if they are using hormone treatment for more than five years,” they continued. “The absolute risk of breast cancer in transgender people is still low in this study, and, more importantly, is not increased compared with cisgender women. We believe therefore that awareness in both doctors and transgender people is of more importance than the start of screening at a younger age or intensifying available screening, even though the median age at diagnosis in the current study was lower than in cisgender women. Besides, discontinuation of hormone treatment in older transgender people can be considered, which might from then decrease the risk of breast cancer. Trans women and trans men who have not had a mastectomy are advised to undergo the same intensified breast surveillance as their close female relatives if the risk of breast cancer is increased because of a familial predisposition. It is important to remember that transgender people who changed their legal sex might not be automatically invited for population-based screenings, including breast cancer screening.”

What this means for you

If you are a transgender woman taking hormones, this study suggests that your risk of breast cancer is higher than a cisgender man, but lower than a cisgender woman. The researchers recommend that you have screening mammograms every other year starting at age 50. It’s a good idea to talk to your doctor about your personal risk of breast cancer and develop a screening plan that is best for your unique situation.

If you are a transgender man taking hormones, this study suggests that your risk of breast cancer is lower than a cisgender woman. If you have not had a double mastectomy, the researchers recommend that you have screening mammograms every other year starting at age 50. It’s also a good idea to talk to your doctor about your personal risk of breast cancer and develop a screening plan that is best for your unique situation. If you have legally changed your sex, you may not receive automatic breast cancer screening invitations, so it makes sense to work with your doctor to develop a plan.

For more information on mammograms, including where to get one, visit the Breastcancer.org Mammograms pages.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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