MDB-20. Toxicity Profile of Two Chemotherapeutic Regimens Adopted From Cog A9961 and Acns0331 for Standard-Risk Medulloblastoma, a Comparative Study

BACKGROUND Medulloblastoma (MB) is classically treated with surgery, irradiation, and chemotherapy (CTH). Cisplatin-based CTH regimens for standard-risk (SR) MB entail significant toxicities particularly ototoxicity which adversely affect patients’ quality of life. We compared the toxicity profile of two regimens in terms of grade 3 or 4 ototoxicity, hematologic toxicity, hepatotoxicity, nephrotoxicity, and neurotoxicity. METHODS SR-MB patients enrolled at Children Cancer Hospital-Egypt (57357) between January 2016 and December 2019 (cohort A) received adjuvant CTH adopted from COG-A9961 protocol (regimen A; 8 cycles of vincristine, cisplatin, and CCNU; cumulative cisplatin dose 600 mg/m2). Starting from January 2020 (cohort B), patients received CTH adopted from ACNS0331 protocol (9 cycles; 2 cycles of vincristine, cisplatin, CCNU followed by 1 cycle of cyclophosphamide and vincristine, for 3 rounds; cumulative cisplatin dose 450 mg/m2). Toxicity grading was done using Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. RESULTS enrolled patients (n=168; cohort A = 112; 67% and cohort B = 56; 33%). Cohort A had significantly higher rate of grade ≥3 ototoxicity at some point during treatment (27% vs 3.6%, p <0.001). Similarly, cohort A had higher grade ≥3 neurotoxicity (26% vs 12%, p =0.046), anaemia and thrombocytopenia (72% vs 56%, p =0.04). Cumulative rate of leukopenia was very high in both cohorts, 98% of all patients, while the rate of febrile neutropenia was much lower in cohort A (38% vs 67%, p <0.001). No toxic deaths were observed in both cohorts. There was no difference in grade ≥3 nephrotoxicity nor hepatotoxicity between the 2 cohorts. The 2-year OS for cohort A and B were 96.4% and 86.6%, respectively, p=0.11. Similarly, the 2-year EFS were 92.9% and 86.8%, p=0.29. CONCLUSION adjuvant CTH from ACNS0331 protocol showed a better toxicity profile particularly for ototoxicity compared to A9961 CTH regimen, while maintaining comparable survival.