Effect of high-dose chemotherapy with autologous stem cell rescue (HDC-aSCR) on outcome in ovarian small-cell carcinoma, hypercalcemic type (SCCOHT): Prospective series from the French Rare Gynecologic Malignant Tumors Network (TMRG)

6023 Background: Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), is a rare and rapidly lethal disease affecting young women with over half dying within 2 years of diagnosis. We previously reported improved outcomes with cytoreductive surgery followed by HDC-aSCR in a prospective study, but these encouraging results needed to be confirmed in an independent and larger cohort. Methods: Between 2008 and 2019, out of 44 patients (pts) diagnosed with centrally confirmed SCCOHT in 16 referent centers of the TMRG network, 38 were treated prospectively according to the French recommendations of the network with complete surgery (primary or after neoadjuvant chemotherapy), 4 to 6 cycles of PAVEP chemotherapy (cisplatin, doxorubicin, vepeside, and cyclophosphamide), and for pts with complete response (CR), HDC-aSCR, followed by pelvic radiotherapy. The 6 patients who could not receive PAVEP (unfit or diagnostic delay) relapsed and died rapidly. The primary endpoint was the event-free survival (EFS) in the intention-to-treat cohort. Results: Median age at diagnosis was 33 years (14-76). 13 pts presented with FIGO stage I, 17 stage III and 6 stage IV, 2 unknown. Median follow-up was 55.5 months. 34 patients achieved CR with CT + surgery and 30 received HDC-aSCR (40%, 47% and 10% with stages I, III and IV diseases respectively) and 21 received also pelvic radiotherapy. Median overall and event-free survival was 36.4 and 15.9 months respectively, and 2-years event-free survival rate was 40% (CI95% 25-56). Median OS was respectively not reached, 18 and 9.6 months for FIGO I, III and IV patients. Among the pts (N = 14) who did not receive HDC-aSCR (rapid progression during or after PAVEP), the 2-yr EFS was 0% compared to 50.5% for the 30 patients receiving HDC. In multivariate analysis, HDC was significantly correlated with better outcomes (p < 0.001). For the 21 patients receiving also pelvic radiotherapy, 57% (12/21) are free of recurrence at 4 years. Grades 3/4 adverse events were frequent (78%) but, in most cases, manageable, although one toxic death (3%) occurred during HDC (fungal septic shock). Conclusions: Treatment of SCCOHT, with intensive multimodal therapy, is associated with a 40% 2-yr event-free survival. However, this protocol is associated with significant toxicity and should be restricted to good performance status patient and expert centers.