7609 Androgen Receptor Positive DCIS in a Transmasculine Individual on Testosterone Therapy

Abstract Disclosure: J. Kelly: None. B. Cohen: None. Introduction: The rate of breast cancer in transgender men is lower than in cisgender women, perhaps due to lower estrogen levels in the setting of suppression from exogenous testosterone, lack of clear guidelines on screening after top surgery, and increase in mastectomies. However, the impact of testosterone therapy on existing breast cancer is not known. Concerns regarding use of testosterone in patients with breast cancer include the potential for conversion of testosterone to estradiol, as well as direct androgen receptor (AR) stimulation. However, for some patients, hormone therapy is lifesaving and stopping gender affirming hormone therapy (GAHT) will negatively impact patient well-being. This creates a challenging clinical scenario when transgender patients on testosterone are diagnosed with breast cancer.Case Presentation: We present a case of a 29-year-old self-identified transmasculine nonbinary individual (assigned female at birth) who underwent chest reconstruction surgery after several months on daily transdermal testosterone therapy. A 4 cm DCIS ER+/AR+ with possible micro invasion was incidentally noted on pathology. They had no family history of breast cancer. The patient underwent chest MRI which was negative for persistent disease. The treating oncologist did not recommend Tamoxifen. The patient chose to discontinue testosterone therapy due to uncertainty regarding future breast cancer risk. However, due to worsening depression and fatigue, the patient chose to resume GAHT after receiving counseling of possible risk, though likely low, of cancer recurrence. Given that they had undergone bilateral mastectomy which, unlike chest reconstruction surgery where some breast tissue is left for contouring, all breast tissue was removed and given that chest MRI was negative for disease, cancer recurrence was felt to be low. Furthermore, though AR positivity was noted, the clinical implications are unclear and it is not known whether testosterone would stimulate tumor growth or potentially have antagonistic effects on ER signaling. Additionally, any stimulatory effects of AR signaling may be balanced by androgen suppression of gonadotroph production and reduction in estrogen production; this is more clearly associated with stimulatory effects on cancer growth. And finally, the potential risks of therapy must be weighed against the benefits provided to the patient’s well-being and mental health. Ultimately, the patient resumed testosterone therapy and has been doing well.Teaching Point: This case illustrates the uncertainties regarding the management of gender affirming testosterone therapy in patients with DCIS or breast cancer. It also highlights the need for a patient centered approach to decisions regarding changes to GAHT, to appropriately weigh the risks and benefits of continuing therapy. Presentation: 6/2/2024