Supplementary Material for: Complexities in Adjuvant Endocrine Therapy for Breast Cancer in Female-to-Male Transgender Patients

Introduction: Managing breast cancer in female-to-male (FtM) transgender patients is complicated and challenging. Androgens play a crucial role in the development of secondary sexual identity in FtM transgender patients, but their effectiveness in breast cancer remains unclear. Furthermore, the considerations for adjuvant endocrine therapy in this population are highly intricate and warrant thorough discussion. Case Presentation: We describe the case of a 44-year-old FtM transgender diagnosed with breast cancer 3 years after initiating androgen receptor agonist therapy as part of his gender identity transition. After mastectomy, adjuvant endocrine therapy was initiated, consisting of a combination of an aromatase inhibitor and a gonadotropin-releasing hormone agonist, along with a cross-sex hormone. Conclusion: Estradiol levels were significantly reduced, and male-typical levels of sex hormones were attained.