RTHP-08. RE-EVALUATING THE SEQUENCING OF RADIOTHERAPY AND CHEMOTHERAPY IN PEDIATRIC MEDULLOBLASTOMA

BACKGROUND: Standard treatment for medulloblastoma in children over age 3 includes resection and radiotherapy, followed by chemotherapy. Some studies have found disease control decrements if chemotherapy was delivered before radiotherapy. However, these studies recommended radiation interruptions for hematologic toxicity, which were more severe in children receiving chemotherapy prior to craniospinal radiotherapy. We report outcomes of pediatric medulloblastoma patients treated post-operatively with radiotherapy-first (RT1) or chemotherapy-first CT1). POPULATION/ METHODS: 206 patients age 2–23 years with medulloblastoma were treated with proton radiotherapy from May 2000 to December 2016. We analyzed the effect of sequencing radiotherapy first (n=164) or chemotherapy first (n=42) after surgery on event-free (EFS) and overall survival (OS) controlling for known risk factors. RESULTS: Median follow-up was 5.8 years. Children who received CT1 sequencing were younger (p