GCT-33. A PHASE 2 TRIAL OF RESPONSE-BASED RADIATION THERAPY FOR PATIENTS WITH LOCALIZED CENTRAL NERVOUS SYSTEM GERM CELL TUMORS: A CHILDREN’S ONCOLOGY GROUP (COG) STUDY. IMPACT OF RAPID CENTRAL RADIOTHERAPY REVIEW ON RADIOTHERAPY QUALITY AND PATTERN OF FAILURE FOR NON-GERMINOMATOUS GERM CELL TUMORS

BACKGROUND COG ACNS 1123 tested reduced radiotherapy (RT) for non-metastatic, non-germinomatous germ cell tumor (NGGCT) patients. The impact of central review on quality of RT and pattern of failure for NGGCT patients is evaluated. METHODS Patients who achieved a complete response (CR) or partial response (PR) to induction chemotherapy were eligible for reduced dose and field RT of 30.6 Gy whole ventricular field (WVI) and 54 Gy tumor-bed total dose. An online contouring atlas was available. Within three days of RT start, WVI plans were submitted for rapid central review. Within one week of RT completion, the complete RT record was submitted. Brain and spine MRIs of relapsed patients were centrally reviewed. RESULTS Between 5/2012–9/2016, 107 eligible patients were accrued and 70 met reduced RT criteria. Rapid RT review was performed for 49 (70%) of 70 patients. Forty-four (89.8%) required no modification. All modifications were completed and plans became compliant. Final central review was performed for 66 evaluable patients: 62 (94%) were per protocol; there were 2 major (1 dose and 1 target) and 2 minor deviations. Eight patients progressed; none had deviations. Median time to progression was 3.54 months (range: 1.7–19.1) from RT start. All failures had a spine component; two also had cranial component: one local progression (within the RT boost volume) and one leptomeningeal disease. CONCLUSION Providing an online contouring atlas and performing a rapid central review lead to high quality radiotherapy on this prospective trial. The deviations did not contribute to the pattern of failure.