Comparison of Severe Toxicities Following High Dose Methotrexate Administration By Demographics and over Time in Pediatric Patients with Acute Lymphoblastic Leukemia

Background: Methotrexate (MTX) is a cornerstone of therapy for pediatric patients with acute lymphoblastic leukemia (ALL). Administration of high dose (HD) MTX requires hospitalization and concurrent intravenous fluids and leucovorin while awaiting drug excretion. HDMTX has been associated with acute adverse events (AEs), such as mucositis, neurotoxicity, and myelosuppression, that can impact quality of life and ability to administer subsequent chemotherapy. There are limited data evaluating differences in AEs after HDMTX among demographic groups. Objective: The objective of this study was to describe AEs for patients receiving HDMTX (defined as >500 mg/m2 to account for dose reductions from protocol dosing) and to compare rates by age, race, ethnicity and dose number using a multicenter cohort. Methods: A multi-center retrospective study collected data on pediatric ALL patients ages 0-21 years at diagnosis who received at least one dose of HDMTX at Children's Healthcare of Atlanta or Cincinnati Children's Hospital Medical Center from January 2010 through December 2020. Demographic (age, sex, race, ethnicity) and clinical (vital status, Down Syndrome, HDMTX doses) variables were manually abstracted from the electronic medical record. Algorithms were developed a priori based on Common Terminology Criteria for Adverse Events v5 to identify the presence and grade of targeted AEs after HDMTX administration. The following AEs were abstracted for the time period from each HDMTX dose until the next HDMTX or other chemotherapy administration: mucositis, neurotoxicity, neutropenia, and thrombocytopenia. Only grade 4 neutropenia and grades 3-4 thrombocytopenia were collected. Institutional review board approval was obtained at each site. Descriptive and inferential statistics, including chi-square, Fisher's exact test, and generalized estimating equations (GEE) as appropriate, were calculated to evaluate differences in AEs by dichotomized age (