MDB-30. Improved Survival with 36Gy Craniospinal Radiation for M1-M3 Medulloblastoma on the Proton/Photon Consortium Registry (PPCR)

Abstract Purpose/Objective(s) To report outcomes for disseminated Medulloblastoma (stage M1-M3) who received radiation (RT) on the Pediatric Proton/Photon Consortium Registry (PPCR). Materials/Methods 71 patients were included with either M1 (6), M2 (21), or M3 (44) Medulloblastoma on PPCR. Survival (OS, Overall; EFS, Event Free) analyses were performed using the Kaplan Meier method and log rank p-values from RT start. Median follow up was calculated using the reverse Kaplan Meier method. Results Median age at RT was 7.5 years (range 2.4-21.89) and the median follow up was 4.3 years. Histology was classic (52), diffuse anaplasia (12), focal anaplasia (5), desmoplastic nodular (1), or other (1). Treatment included surgery, chemotherapy with or without stem cell support, and RT. 54 patients had gross total resection (GTR) or near total resection (NTR); 14 had subtotal resection (STR). Pre-RT chemotherapy was given in 69 (97.1%) patients; 23 had myeloablative chemotherapy with stem cell support. The 5 and 10-year OS of the entire cohort were 73% and 65%, and 5 and 10-year EFS were 65% and 59%. Patients with progression prior to RT (10 patients) had inferior OS (5-year OS 44%) compared to patients without progression pre-RT (5-year OS 78%, p = 0.045). There was a trend for better OS (p = 0.07) and improved EFS (p = 0.043) for M2 stage. GTR/NTR did not impact OS (p = 0.75) or EFS (p = 0.97) compared to STR. Craniospinal (CSI) radiation (70 patients, 99%) doses were: £ 23.4Gy (11.4%), 23.5Gy-36Gy (11.4%), or ³ 36Gy (74.3%). Patients receiving CSI ³ 36Gy had superior OS (p = 0.043), with 5 and 10-year OS of 82% and 71% compared to 5 and 10-year OS of 52% and 52% for lower dose CSI. Conclusion Full dose CSI (36Gy) for M1-M3 medulloblastoma was associated with excellent long-term survival this series, whereas lower dose CSI and progression prior to RT had inferior outcomes.