Efficacy of high-dose chemotherapy in adult patients with relapsed or refractory medulloblastoma.

2087 Background: Adult medulloblastoma (MB) is rare, and there is no standard salvage approach for relapsed or refractory cases. High-dose chemotherapy (HDC) with autologous stem cell transplantation (ASCT) has shown potential, but evidence in adults remains limited. This study evaluated the response rate, survival and toxicity after HDC with ICE regimen followed by ASCT in MB, with further focusing on post-ASCT response and pretransplant intracranial residual disease (ICRD). Methods: We retrospectively analyzed adult patients with relapsed/refractory MB who underwent HDC with the ICE regimen followed by ASCT. Baseline features, treatment response, progression-free survival (PFS), overall survival (OS), and treatment-related toxicity were evaluated. Subgroup analyses focused on post-ASCT response and pretransplant intracranial residual disease (ICRD). Results: The study included 23 patients (median age: 24 years; male: 52%, with 43% classic subtype and 61% pretransplant ICRD). The overall and complete response (CR) rates to HDC was 73.9% and 48%, respectively. The median PFS was 12.8 months, and OS was 45.1 months, with 2-year PFS and OS rates of 31% and 63%, respectively. Patients achieving CR after ASCT had significantly longer OS (NR vs 16.4 months; HR, 0.15; 95% CI, 0.03–0.72; P=.02), corresponding to an 85% reduction in mortality risk compared with non-CR patients. OS was markedly shorter in patients with pretransplant intracranial residual disease compared with those without (22.5 vs. 74.0 months; HR, 7.08; 95% CI, 1.3–36.3; p = 0.008).The large cell/anaplastic subtype remained the poorest prognostic group despite ICE induction. Toxicity was dominated by universal grade 4 myelosuppression and febrile neutropenia, but no transplantation-related mortality occurred. Conclusions: This study showed that HDC with ICE followed by ASCT is feasible in adults with relapsed/refractory MB, with encouraging survival and manageable toxicity. Pretransplant ICRD clearance and achievement of CR were major prognostic determinants, while non-CR patients remained at high risk, highlighting the need for treatment intensification in this subgroup.