ID #396 High-Dose Chemotherapy with Autologous Stem Cell Rescue in Children under 5 Years of Age with Central Nervous System Embryonal Tumors: Results from a Prospective Middle-Income Country Cohort

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Abstract High-dose chemotherapy (HDCT) with autologous stem cell rescue (ASCR) has been employed to mitigate long-term side effects of radiotherapy (RT) and improve survival of central nervous system (CNS) embryonal tumors in infants. Objective Characterize a cohort of patients treated with a transplant-based strategy in a middle-income country. Methods Prospective study supported by Federal funding from National Oncological Care Support Program for children under five years-old with CNS embryonal tumors. Results From 2016-2019, thirty-six patients were included: Twenty-two medulloblastomas (MB), six atypical teratoid/rhabdoid tumors, one pinealoblastoma, and seven other CNS embryonal tumors. Among the MB group, mean age was 2.5 years (1.5-4.8y), 13 were male. Eighteen had complete resection, fifteen had no metastasis (M0). Among non-MB patients, mean age was 2.7 years (0.7-2.9y), 11 were female. Nine had complete resection, 12 were M0. According to molecular subgroups, event-free-survival (EFS) rates at 2 and 5 years for SHH were 76.9% and overall (OS) 92.3%. For the non-WNT/non-SHH subgroup, EFS at 2 and 5 years were 33.3% and 22.2%, while OS were 66.7% and 55.6%, respectively. Both relapsed SHH patients had p53>50% on immunohistochemistry. Two SHH and five non-WNT/non-SHH patients were rescued with craniospinal RT and except for two non-SHH patients with metastatic relapses, the others are still alive without disease. Death occurred in one SHH patient due to meningitis, and two non-WNT/non-SHH during induction due to sepsis and disease progression. For all non-MB cases, EFS and OS at 2 and 5 years were 28.6%/19.0% and 42.9%/32.1%. All patients presented with mucositis/typhlitis and febrile neutropenia grade 3-4 during HDCT/ASCR. Conclusion HDCT/ASCR can be conducted in well-structured centers, even in countries with less resources as Brazil. Except for those with SHH-MB, the prognosis for infants with non-SHH MB and other CNS-embryonal tumors remains poor, highlighting the need for new treatment approaches.

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