MB-78: SPANISH EXPERIENCE IN PEDIATRIC MEDULLOBLASTOMA

PURPOSE: Medulloblastoma, the most common malignant primary brain tumor in children, accounts 20% of pediatric CNS cancers. In Spain, MB represents 2-5 cases per 100.000 children (0-14 yrs). The present study aimed to characterize a large series of Spanish MB samples combining clinical, pathological and molecular data. METHODS: Centralized immunohistochemistry (nuclear β-catenin and p53) and FISH (MYC and MYCN) analyses were performed on FFPE tissues from 119 patients aged 0-17 yrs, recruited from 18 hospitals since 1997 to 2015. All patients were treated following SIOP collaborative brain tumor protocols. Clinical data including follow-up were collected. RESULTS: The mean age at diagnosis was 6.5 yrs; 26% (0-3 yrs), 71% (4-15 yrs) and 3% (>15 yrs). Males were predominant (60%). The most common histology was classical (60%), followed by desmoplastic/nodular (30%) and large cell/anaplastic (LCA) (10%). MYC/MYCN amplification was detected in classical (11%) and LCA (38%) tumors and was associated with poor clinical outcome (exitus 62.5% and 60%, respectively). Nuclear staining of β-catenin was identified in three classical cases with good prognosis and one LCA patient (exitus). P53 protein nuclear expression was positive in classical (14%), desmoplastic/nodular (8%) and LCA (23%) and was associated with a worse five-year overall survival (48 vs. 71 months). Metastatic disease combined with classical histology and localized LCA tumors were associated with poor outcome. CONCLUSION: In this series, MYCN/MYC amplification and p53 overexpression are associated with high-risk status and poor outcome. Metastatic disease increased the risk of death by MB. Our experience supports data from other studies.