Female hormones increase breast cancer risk

Breast cancer cells under the microscope

Trans women who take hormones increase their risk of developing breast cancer, but the risk is still less than for cis women, according to a new study.

The research discovered that taking hormones means trans women are far more likely than cis men to develop the cancer. They are still much less likely to develop it than cis women.

Trans men significantly reduce their risk of breast cancer when they take testosterone to transition.

cancer strikes younger

If trans people on hormones do develop breast cancer it’s likely to happen at a younger age than a cis woman would expect.

The research, by the University Medical Centre in Amsterdam, is published in this week’s British Medical Journal.

The university’s gender clinic believe they look after 95% of trans people accessing gender services in the Netherlands.

They followed 2,260 trans women and 1,229 trans men.

All of the people in the study were all taking hormones to transition.

altered risk

Fifteen of those trans women were found to have breast cancer. The researchers calculated that this was almost 50 times higher than the number of cases they would expect in cis men, but less than they would expect in cis women.

Breast cancer was also found in four of the trans men. That’s higher than would expected among cis men, but lower than the number to be expected among the same number of Dutch cis women.

Mammogram screening for breast cancer

cancer younger

If trans women and trans men do develop breast cancer it’s likely to happen when they are much younger than would be expected for cis women, the researchers found.

The typical age for a breast cancer diagnosis for a trans woman was 52 years, and it was 46 years for trans men. The average age for diagnosis in a Dutch cis woman is 61.

Breast cancer is the most common form of cancer in cis women, and 12% of the population can expect to have it. It is much rarer among men, less than one in a thousand cis men are found to have the disease.


The researchers say their results show that trans women, and trans men who have not had a mastectomy, should be screened as part of the general screening programme for women: “These results suggest that breast cancer screening guidelines for cisgender people are sufficient for transgender people using hormone treatment”.

Picture credits: Cancer cells from Wiki Commons, Mammogram from Wiki commons.

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