CTNI-56. A MULTI-INSTITUTIONAL RETROSPECTIVE SERIES OF ADULT-ONSET MEDULLOBLASTOMA

Abstract

Abstract Adult-onset medulloblastoma is a rare tumor for which limited data exists. Current treatment is based on data from childhood medulloblastoma. We present a retrospective cohort of 130 consecutive patients age ≥ 18 years and treated at the University of Washington (N = 61), University of Florida (N = 50), and Stanford University (N = 19), from 2000-2021. Median duration of follow-up was 57.3 months. Patients were 57.7% male (75/130), with median age at diagnosis of 29 years. 5 and 10-year overall survival were 78.9% and 67.6% and no recurrence was seen beyond 10 years. 31/130 (23.8%) patients had Chang M1 or greater disease and molecular typing was available for 41/130 patients. There was no improvement in progression-free survival (PFS) or overall survival (OS) either in patients who received proton therapy or those who received concurrent vincristine. There was a trend favoring longer OS in patients receiving radiotherapy within 6 weeks of surgery. A trend towards shorter OS in patients receiving a higher craniospinal radiation dose ( > 30Gy) likely reflected accurate clinical risk stratification. There was no improvement in OS or PFS for adjuvant chemotherapy overall, but patients receiving ≥ 5 cycles had improved PFS (HR 2.10, 95% CI = 1.19 - 3.90, p = 0.038) and a trend to improved OS (HR 2.07, 95%CI = 0.81-5.25, p = 0.125). After first progression, median OS was 20.7 months and both 5 and 10-year survival were 24.8%. We conclude that surveillance past 10 years may be unnecessary and that 1 in 4 patients achieve long-term survival after first relapse. Within the confines of a retrospective study, these data suggest equivalence between proton and photon radiotherapy, no benefit to concurrent vincristine, and that at least 5 cycles of adjuvant chemotherapy are required to delay progression.