Trans women and transfeminine people taking HRT are far less likely to develop prostate cancer

Zinnia JonesConcerns over supposedly cancer-causing effects of cross-sex hormone therapy are an area in which public alarm has often pulled far ahead of the facts on transition and transgender health. For instance, in 2019, the Telegraph breathlessly reported that the “risk of breast cancer rises 46 times for trans women after hormone therapy”. What this framing omitted is that the study found trans women had a 70% lower likelihood of developing breast cancer compared to cis women, that the “absolute risk of breast cancer in transgender people remains low”, and that “following breast cancer screening guidelines for cisgender people seems sufficient for transgender people using hormone treatment” (de Blok et al., 2019).

Abigail Shrier, in her recent book Irreversible Damage: The Transgender Craze Seducing Our Teenage Daughters, referred to a “suspected risk” of uterine and endometrial cancer in trans men taking testosterone, then upgraded this suspicion to the overt claim that testosterone “can raise the risk of endometrial cancer significantly” in an interview at the Heritage Foundation’s Daily Signal; Jonathon Van Maren’s review of Shrier’s book makes the completely separate claim that puberty-blocking medications used for trans adolescents “create a higher risk of” cancer, an assertion that was not made by Shrier.

Meanwhile, UCSF Transgender Care states that trans men on testosterone are at a low risk of endometrial cancer and no evidence suggests that trans men have a greater risk of ovarian cancer, and that because these risks are not elevated, the surgical removal of the uterus or ovaries solely for the prevention of these cancers is not recommended (Wesp, 2016). The National LGBT Cancer Network has pointed out that numerous factors place trans men at greater likelihood of dying of ovarian cancer, including being less likely to experience protective factors against ovarian cancer such as having been pregnant and having used hormonal contraceptives, and lower utilization of screening that can detect ovarian cancer at an earlier stage – but use of testosterone is not among these risk factors for cancer. And although GnRH agonists, the long-acting medications used as puberty blockers for trans adolescents, are also used as part of androgen deprivation treatment for prostate cancer – a fact that was misconstrued by right-wing outlets to claim that these treatments were “linked” to “thousands of deaths” – this class of drugs does not appear to cause cancer.

But this pattern of claim and counterclaim, “hormones give trans people cancer” versus “hormones don’t give trans people cancer”, doesn’t fully explore another side of the universe of possibilities here: What if treatment with hormone therapy prevents cancers that trans people would have otherwise developed?

A recent study of trans women in the Netherlands suggests that when it comes to the likelihood of suffering from prostate cancer, this is indeed the case. Even after receiving genital surgery, trans women still have a prostate, as removing this organ can lead to incontinence and negatively impact quality of life. de Nie et al. (2020) studied all trans women who received transition treatment and hormone therapy, including estrogen and antiandrogens, at Amsterdam’s VU University Medical Center from 1972 to 2016, and looked for any cases of prostate cancer. 2,281 trans women were included in the study, over a total followup time of 37,117 years (7 to 24 years after each woman started HRT), and over this period, 6 cases of prostate cancer were identified. Compared to rates of prostate cancer in the general population of cis men in the Netherlands, it was found that trans women on HRT have only 20% the risk of cis men of developing prostate cancer, with a 95% confidence interval of 8-42%. In other words, trans women on HRT are 80% less likely to get prostate cancer.

This also held true in trans women who’d had their testes removed as part of orchiectomy or vaginoplasty, who were only 17% as likely as cis men to develop prostate cancer. However, because trans women in the study may have switched between many different dosages and routes of administration of estrogen over the course of receiving HRT, and generally used cyproterone acetate as an antiandrogen with only rare use of spironolactone, this study was not able to identify any particular hormonal regimens associated with a higher or lower likelihood of developing prostate cancer. UCSF Transgender Care has recommended that trans women follow the same prostate cancer screening guidelines as cis men, and that in trans women who’ve had vaginoplasty, digital examination of the prostate may be more easily achieved via the neovagina (Wesp, 2016).

These results are not necessarily surprising, as the growth of prostate cancer is generally promoted by the availability of androgens such as testosterone, and it has been treated using estrogenic or antiandrogenic medications in cis men. And this is not the only case in which transition treatments offer benefits rather than risks in influencing the likelihood of cancer. de Blok et al. (2019) found that not only did trans women have a 70% lower risk of breast cancer than cis women, but trans men also had an 80% lower risk than cis women. Routine histopathological examination of breast tissue removed during transmasculine chest reconstruction surgery represents an opportunity for screening for breast malignancies (Van Renterghem et al., 2018), and in at least one case, initiation of HRT in a trans woman served to reveal the presence of testicular cancer (Elshimy et al., 2020). The relationship between gender-affirming medical treatment and cancer is not as simple as the “A leads to B” narrative commonly pitched by anti-trans activists – and sometimes, transitioning might even give you un-cancer.

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About Zinnia Jones

My work focuses on insights to be found across transgender sociology, public health, psychiatry, history of medicine, cognitive science, the social processes of science, transgender feminism, and human rights, taking an analytic approach that intersects these many perspectives and is guided by the lived experiences of transgender people. I live in Orlando with my family, and work mainly in technical writing.
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