Cancer Risk with Hormone Therapy

The Dutch cohort study by De Blok and colleagues (2019, BMJ) investigated breast cancer incidence among more than two thousand trans women receiving feminising hormone therapy.

Breast Cancer in Trans Women

The Dutch cohort study by De Blok and colleagues (2019, BMJ) investigated breast cancer incidence among more than two thousand trans women receiving feminising hormone therapy. The incidence was higher than among cisgender men, but lower than among cisgender women. The tumours were usually hormone receptor-positive.

Breast Cancer in Trans Men

In trans men who have not undergone a mastectomy, the risk of breast cancer remains as long as breast tissue is present. In trans men who undergo a mastectomy, a residual (lower) risk remains, comparable to that following prophylactic mastectomy.

Other Cancers

More research is needed on other types of cancer (prostate cancer, cervical cancer when the cervix is retained, and ovarian cancer). International guidelines recommend tailoring cancer surveillance to the organs present and the hormone profile.

The Amsterdam Figures

In De Blok's study, fifteen cases of invasive breast cancer were found among 2,260 transgender women. That is dozens of times more than would be expected in men, and approximately one-third of what would be expected in women. The tumours developed after a relatively short treatment duration. Among 1,229 transgender men, four cases were found, fewer than would be expected in women. An explanation of the figures on oestrogen and breast cancer can be found at genderrisico.nl.

Prostate and Meningioma

The prostate remains present after vaginoplasty. Prostate cancer occurs less often in transgender women than in men, probably because testosterone is suppressed, but it cannot be ruled out. The drug cyproterone acetate is associated with meningiomas when used long term at higher doses; these are usually benign tumours of the membranes surrounding the brain. The European Medicines Agency therefore restricted the use of the drug in 2020.

Population Screening

Invitations for population screening for breast and cervical cancer are sent based on the sex recorded in the population register. A trans man who is registered as male but still has a cervix or breast tissue will not receive an invitation and must register himself. A trans woman who is registered as female will be invited for breast screening. Discuss with your GP which checks are appropriate in your situation. See mastectomy, oestrogen and hormone therapy.