BREAST CANCER IN TRANS WOMEN

Transwomen on hormone treatment face a much higher risk of breast cancer than cisgender men but a lower risk than cisgender women, according to new findings.

"Transwomen who started hormones have a higher risk for breast cancer than before. Therefore, they should be advised to undergo breast-cancer screening as advised to women in general," Dr. Martin den Heijer of VU University Medical Centre in Amsterdam, the study's senior author, told Reuters Health by email.

While the study found a lower risk of breast cancer for trans men than cisgender women, doctors should be aware that breast cancer still can occur in transmen after mastectomy," he added.

Dr. den Heijer and his colleagues analyzed data on 2,260 transwomen (33,991 person-years) and 1,229 trans men (14,883 person-years) who received gender-affirming hormone treatment at their tertiary gender clinic.

Transwomen were on hormone treatment for a median 18 years and transmen for 15 years, the researchers report in The BMJ, online May 14. Invasive breast cancer was diagnosed in 15 transwomen and four trans men.

Breast-cancer risk for transwomen was 46 times higher than for the general Dutch population of cisgender males (standardized incidence ratio, 46.7), a significant difference. But it was significantly lower than would be expected in cisgender women (SIR, 0.3).

Transmen's breast-cancer risk was lower than that of cisgender women (SIR, 0.2).

The absolute risk of breast cancer in transgender people is still low in this study, and, more importantly, is not increased compared to cisgender women," Dr. den Heijer and his team write. We believe therefore that awareness of 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."

Transwomen who change their legal sex are invited for breast-cancer screening in the Netherlands, Dr. den Heijer noted. Without such a change, however, they are usually not invited and often they do not know nor are (they) informed about the need for screening."

He and his colleagues plan to investigate the long-term effects of gender-affirming treatment on the risk of other diseases, including other types of cancer.