Prognostic significance of molecular subgroups of medulloblastoma in young children receiving irradiation-sparing regimens

Purpose Irradiation-avoiding strategies have been used with relative success in the treatment of infants and young children with medulloblastoma. While advances in cancer genomics have significantly improved our understanding of the tumor biology of medulloblastoma allowing for improved prognostication and risk-stratification, the molecular subgroup-specific outcomes of infants and young children with medulloblastoma treated with irradiation-avoiding strategies remains unknown. Methods Molecular and clinical features of children with medulloblastoma treated with irradiation-avoiding strategies at Children’s Hospital Los Angeles were analyzed. Molecular subgrouping of these patients was determined using a 31-gene Taq Man Low Density Array signature. Survival analyses were conducted based on 3 molecular subgroups (SHH, Group 3, and Group 4). Results Twenty-eight patients with medulloblastoma received irradiation-sparing regimens and were included in this analysis. Patients were divided into SHH (n = 16), Group 3 (n = 3) and Group 4 subgroups (n = 9). Subgroup specific 5-year progression-free and overall survival was 81.2% (95% CI 52.5–93.5) and 93.7% (95% CI 63.2–99.1) for SHH, 0% and 0% for Group 3 and 0% and 44.4% (95% CI 13.6–71.9) for Group 4. Conclusion The majority of young children with SHH-subgroup medulloblastoma can be treated effectively with irradiation-sparing regimens. Our results support the use of chemotherapy-only strategies for upfront treatment of young children with SHH medulloblastoma, while demonstrating the urgent need for intensification/augmentation of treatment for patients with group 3/4 medulloblastoma.