5547 Background: Sertoli-Leydig cell tumors (SLCT) are rare ovarian sex cord-stromal tumors which occur primarily in adolescents and young adults and are associated with DICER1 pathogenic variants. Methods: Informed consent for participation in the International PPB/ DICER1 or OTST Registry was obtained. When available, pathology was centrally reviewed. Staging was evaluated by Registry review using the International Federation of Gynecology and Obstetrics (FIGO) classification system. Results: Eighty-three patients with stage I SLCT were enrolled. Median age at diagnosis was 15 (range 1-60) years. Most (57/83) patients had germline DICER1 testing; 35/57 (61%) had germline pathogenic variants. Fifty-six patients had Ia and 27 had Ic SLCT. The distribution of patients receiving chemo based on histology and stage is displayed in Table. One patient with poorly differentiated stage Ia SLCT with sarcomatous elements and no chemo at diagnosis recurred 6 months after surgery and died of disease. Three patients with local diagnosis of stage Ia SLCT, with data unavailable for Registry confirmation of stage, developed a subsequent SLCT 33 to 74 months after diagnosis; of these, 2 died, and 1 remains in treatment for recurrence. Available records and molecular testing in these 3 cases have not provided a distinction between recurrent and metachronous disease. Excluding the latter 3 patients, 3-year overall survival was 97.3% for stage Ia SLCT. Six patients with stage Ic SLCT recurred (Stage Ic1=5 and Stage Ic2=1) with a median time to recurrence of 25 (range 3-53) months. In stage Ic1, 18% (2/11) recurred after upfront chemo compared to 33% (3/9) after surgery alone. Of the 5 patients with stage Ic1 disease that recurred, 4 had intermediate and 1 had poorly differentiated SLCT. One patient had sarcomatous elements and 2 received upfront chemo. Two of the 5 patients are alive, neither received upfront chemo. One patient with poorly differentiated stage Ic2 SLCT with sarcomatous elements and no upfront chemo recurred and died of disease. Three-year event free and overall survival were 86.9 and 88.6% for stage Ic SLCT. Four patients had metachronous SLCT in the contralateral ovary confirmed by clinical review or somatic testing at a median time from diagnosis of 33 (range 28-104) months. All 4 have germline pathogenic variants and no evidence of disease at last follow-up. Conclusions: Individuals with early stage SLCT generally fare well, however, ongoing surveillance for recurrence and metachronous disease is indicated. Novel therapies are needed to address recurrent SLCT.[Table: see text]
TERT Gene Fusions Characterize a Subset of Metastatic Leydig Cell Tumors