Iris de Nie

110 C H A P T E R 7 ABSTRACT Objective: To assess the incidence of testicular cancer in trans women (male sex assigned at birth, female gender identity) using gender-affirming hormonal treatment. Materials and Methods: Data of trans women starting hormonal treatment at our gender identity clinic between 1972 and 2017 were linked to the national pathology database to obtain testicular cancer diagnoses. The standardized incidence ratio (SIR) was calculated using the number of observed testicular cancer cases in our cohort and the number of expected cases based on age-specific Dutch incidence rates. Subgroup analyses were performed in testicular tissues send for histopathological analysis at time of bilateral orchiectomy, and when follow-up time exceeded 5 years. Results: The cohort consisted of 3,026 trans women with a median follow-up time of 2.3 years (interquartile range 1.6-3.7). Two testicular cancer cases were identified whilst 2.4 cases were expected (SIR 0.8, 95% CI 0.1-2.8). In addition, one testicular cancer case was encountered in an orchiectomy specimen (0.1%). In the 523 trans women with a follow- up time exceeding 5 years (median 8.9 years, interquartile range 6.4-13.9), no testicular cancer was observed. Conclusion: Testicular cancer risk in trans women is similar to the risk in cis men. The testicular cancer cases occurred within the first 5 years after commencing hormonal treatment, and the percentage of cases encountered at time of bilateral orchiectomy was low. Since no testicular cancer was observed in trans women with a long follow-up time, long-term hormonal treatment does not seem to increase testicular cancer risk.