High Doses of Chemotherapy and Autologous Hematopoietic STEM Cell Transplantation in Patients with Relapsed/Refractory Testicular GERM Cell Tumors. Multicenter Real-World Experience in Argentina.

Introduction: Germ cell tumors (GCTs) are the most common type of cancer in adolescent and young adult males. Most of them are curable with multimodal treatment: platinum-based chemotherapy (CT) + surgery. Patients who fail first-line treatment usually receive salvage CT with response rates between 30 and 50%. High-dose chemotherapy and autologous hematopoietic stem cell transplantation (HDCT) is an effective treatment in this context. Methods: We conducted a multicenter retrospective analysis of patients ≥ 15 years old with relapsed/refractory GCTs who received HDCT in 13 centers of the Argentine Group of Bone Marrow Transplantation and Cellular Therapy (GATMO-TC) from 2010 to 2022. Results: 114 patients were included, with a median age of 32 years (range: 15-58). Most had non-seminoma histology (66%); The primary tumor site was testis (65%), retroperitoneum (17%) and mediastinum (9%). Forty percent (n:46) had unfavorable prognosis according to the IGCCCG score. Eighty-two % received ≥ 2 lines of CT before HDCT, 27% being platinum refractory disease (PRD); and 45% received 2 consecutive course of HDCT (tandem) All patients received carboplatin-etoposide based conditioning regimen. The median engraftment time was 12 days (d) (r8;25) for neutrophils and 15 d (r6;58) for platelets. Bacteremia (25%) and Hepatotoxicity (14.9%) were the most frequent G3-4 adverse event. With a median follow up of 12.6 months (r1-138), 100 pts were evaluable for survival. 12- and 24-months OS was 67%- 64%; and PFS 56%; - 54% respectively. PRD patients had worse OS and PFS. Eighteen patients remained alive and without relapsed beyond 5 years of follow up. Table 1: OS and PFS according to 1st line response. Conclusions: This real world multicentric study demonstrates that patients with refractory/relapsed metastatic GCT are curable by HDCT, being an effective and safe feasible treatment with response rates similar to those described in the literature. Superiority of the tandem approach could not be demonstrated due to the heterogeneity of the sample.