Iris de Nie

119 INCIDENCE OF TESTICULAR CANCER IN TRANS WOMEN USING GENDER-AFFIRMING HORMONAL TREATMENT 7 cohort size and a longer follow-up time, and hereby draw even more reliable conclusions on testicular cancer risk in trans women. Secondly, it was not possible to compare between GAHT protocols, since, on the one hand, many trans women change often between different types of prescribed estrogens over time and, on the other hand, theymostly use cyproterone acetate as antiandrogenic treatment. Furthermore, scrotal ultrasound to screen for the presence of testicular cancer was not routinely performed at initiation and during GAHT, but this was also not the case for the reference population, since guidelines advice against population-based screening. 16 Therefore, we do not expect that this affected our results. In conclusion, this large nationwide cohort study in trans women using GAHT suggests that testicular cancer risk is comparable to the risk in cis men. Furthermore, results from our subgroup analysis in trans women with a long follow-up period, suggest that longer exogenous estrogen exposure does not increase the risk for the development of testicular cancer. This is reassuring for trans women who do not wish, or not have the option, to undergo genital gender-affirming surgery. However, awareness of the presence of the gonads remains important and regular testicular self-examination is recommended.