NCOG-47. CAN YOUNG CHILDREN WITH RELAPSED MEDULLOBLASTOMA BE SALVAGED AFTER INITIAL IRRADIATION-SPARING APPROACHES?

Abstract

Abstract INTRODUCTION Irradiation-sparing approaches are used in young children with medulloblastoma (MB) given the vulnerability of the developing brain to neurocognitive impairment. Limited data are available following relapse for these patients. We aimed to describe the management and outcomes of young children with MB who relapsed after initial treatment without craniospinal irradiation (CSI). METHODS International retrospective study including patients with MB diagnosed between 1995-2017, ≤ 72 months old, initially treated without CSI, who subsequently relapsed. RESULTS Data are available for 66 patients. The median age at initial diagnosis was 27 months (range, 6-72). At diagnosis, 27 patients had metastatic disease. Initial therapy included conventional chemotherapy or with high-dose chemotherapy (HDC) in 30 and 36 patients, respectively. Eight (12.1%) received upfront focal irradiation. Molecular subgrouping was available for 27 (41%) patients. Ten were SHH, five group 3, six group 4 and six others were non-WNT/non-SHH. The median time from initial diagnosis to relapse was 13 months (range, 3-63). Relapse was local, disseminated, or combined in 39%, 32%, and 29%, respectively. The median time to death from relapse was 18 months. Curative intent therapy was given in 53 patients with irradiation (81%), conventional chemotherapy without HDC (40%), and HDC (25%). For patients who received irradiation, 85% received CSI (median dose 33 Gy, 18-41.4) and 15% focal irradiation. Ten patients received chemotherapy without salvage irradiation. The median follow-up time was 44 months (range, 4-255), 33 (62%) patients who underwent curative-intent therapy were alive, including 8/10 SHH, 2/3 group 3, 2/6 group 4, and 4/5 non-WNT/non-SHH. Three of four patients with SHH and treated without salvage radiotherapy are survivors. The 5-year OS for curative intent was 70%. CONCLUSION A substantial proportion of young children who relapse following irradiation-sparing strategies can be salvaged. A proportion of children with SHH MB can be salvaged without salvage radiotherapy.