A Phase 2 Trial of Response-Based Radiation Therapy for Localized Central Nervous System Germ Cell Tumors: Patterns of Failure and Radiation Dosimetry for Nongerminomatous Germ Cell Tumors.
Academic Article
Overview
abstract
BACKGROUND: XX study tested the efficacy of reduced dose and field of radiation therapy (RT) for localized nongerminomatous germ cell tumor (NGGCT) patients who achieved a complete (CR) or partial response (PR) to chemotherapy. Here, we evaluate the quality of RT and patterns of failure for patients eligible for reduced-RT on this phase 2 trial. METHODS: Patients with localized NGGCT with CR/PR post-induction chemotherapy received reduced-RT to 30.6Gy whole ventricular irradiation (WVI) and 54Gy tumor-bed total dose. An atlas was provided to assist with complex RT volumes. Early interventional review was performed for the initial RT plan. Complete RT plans for all patients and images of relapsed patients were centrally reviewed at completion of therapy. RESULTS: Between 5/2012-9/2016, 107 eligible patients were enrolled and 66 achieved a CR/PR after induction chemotherapy (±second-look surgery) and were eligible for reduced-RT. Median follow up was 4.4 years. Median age was 11.0 (3.7-21.6) and 75% were male. Progression-free survival and overall survival at 4 years were 87.9±4.0% and 92.4±3.3% for 66 evaluable patients, respectively. Eight patients relapsed: 6 with isolated spinal relapse and 2 with disease in the brain and spine. After central review, 62 (94%) patients had RT targets contoured and dose delivered per protocol. None of the patients with deviations (n=4) have progressed. CONCLUSIONS: Patterns of failure suggest the spine is at risk for recurrence for localized NGGCT patients who receive reduced-RT after a CR/PR to induction chemotherapy. While survival data are encouraging, the pattern of failure has influenced the next prospective trial design. RT compliance was excellent despite complexity of radiation volumes, suggesting that providing visual guidance in the form of an online atlas contributes to higher quality RT plans.
