MDB-69. Radiological Patterns of Recurrence in Medulloblastoma Subgroups and Correlation With Survival

Abstract BACKGROUND Medulloblastomas can recur in up to one-third of the patients despite optimal therapy. The knowledge of the molecular group can provide clues to the possible pattern of relapse and the course of disease, with therapeutic implications. In the present study, we have identified anatomical locations and radiological patterns of relapse. METHODS AND MATERIALS Patients with a histopathological diagnosis and available subgroups of medulloblastoma with first relapse, treated in a single tertiary care center during 2005-2021 with available magnetic resonance imaging of brain and spine were included in the retrospective study. Statistical analysis was done using Pearson chi-square test and Fisher’s exact test. RESULTS 127 patients were included in the final analysis. Median age at diagnosis was 12 years and time to first recurrence was 21 months. Tumor bed relapse was seen in 49% cases, maximum in SHH subgroup, p0.01. Involvement of the ventricular system (including cisterns and ventricles) was seen in 37% of cases, and was significantly associated (p:0.01) with non-WNT, non-SHH tumours. Leptomeningeal metastasis was seen in 36% of cases, with significant association (p0.01) in group 3 (75% of all group 3 cases) and group 4 tumors (50% of all group 4 cases). Disease in spine was most common in group 3 (65%) and group 4 tumours (71%), p0.01. Hippocampus was involved in 19 cases (15%), mostly in non-WNT, non-SHH (14 cases). Significant difference in survival after recurrence was seen with ventricular, extraventricular metastases with one year survival 83% and 73% respectively, p=0.02. Hippocampal involvement showed significantly decreased survival, one year survival of 37%, p0.01. CONCLUSIONS Leptomeningeal dissemination and diffuse disease were mostly seen in group 3 tumours, indicating their aggressive nature. The lower rates of ventricular relapse and around hippocampus in SHH medulloblastoma provide the opportunity to explore hippocampal avoidance-craniospinal irradiation.