OTHR-16. CONCURRENT USE OF APREPITANT AND IFOSFAMIDE IN PEDIATRIC CANCER PATIENTS

BACKGROUND Aprepitant, a selective neurokinin-1 receptor antagonist, is commonly used for prevention of chemotherapy-induced nausea and vomiting. Its use with ifosfamide is controversial due to the putative risk of potentiating neurotoxicity via inhibition of cytochrome P450 3A4 (CYP3A4). The current literature examining this interaction is inconclusive, and little data exists in pediatrics. We seek to describe a single-institution experience with concurrent aprepitant and ifosfamide administration. METHODS A retrospective review of patients treated with ifosfamide and aprepitant from 2009–2018 was conducted. Data collected included demographics, tumor type, number of days of concurrent therapy, dosing, and documented of neurotoxicity. RESULTS Twenty patients aged 7–21 years (median 17 years) were identified. Diagnoses included thirteen sarcomas and seven CNS tumors (6 germ cell tumors; 1 intracranial sarcoma). Five patients received high dose ifosfamide (>2,000mg/m2/day). The number of concurrent ifosfamide and aprepitant doses ranged from 2–18 (median, 8.5). Only one patient (5%) developed ifosfamide-induced neurotoxicity: a 7-year-old female with a nongerminomatous germ cell tumor who presented with seizures and somnolence. She received methylene blue and returned to her neurologic baseline. She completed her ifosfamide course without incident. She was the only patient to require weight-based aprepitant dosing and to receive the liquid formulation. CONCLUSIONS Aprepitant should be used with caution when administered concurrently with ifosfamide due to the risk of neurotoxicity. However, the incidence of neurotoxicity in this retrospective pediatric cohort was low. This interaction may be more significant in younger patients due to age-related differences in hepatic metabolism, but further study is required.