Breast cancer risk in transgender people receiving hormone treatment.
The best evidence on this subject comes from the University of Amsterdam, in a study published in 2019. The study looked at over 2000 trans-women and over 1000 trans-men receiving hormone therapy. Their health outcomes were followed for between 5 and 23 years from the commencement of treatment.
Most of the trans-women had been treated with a combination of oestrogens and anti-androgens resulting in the development of normal breast tissue. The rate of breast cancer in these trans-women was 8 per 1000 (17/2260), a rate of cancer that was much higher than would be expected for men without hormone treatment.
All of the trans-men had been treated with testosterone tablets, gel or injections. The majority also undergo double mastectomy as part of their gender reassignment surgery, but often keeping the nipples. The rate of breast cancer in trans-men was 4 per 1000 (4/1229), and in 3 of these cases the cancer had arisen despite having had mastectomy surgery many years before.
The conclusion from these statistics is that both trans-women and trans-men need to be breast aware, as both groups are at risk of breast cancer. In addition the NHS breast screening programme offers screening mammography to all trans-women, and also to trans-men who have not undergone double mastectomy. Public Health England has issued guidelines for screening trans people, and so all GPs should be aware of this. All are eligible for screening between 50 and 70 years of age.