UTILITY OF REPEATED DRUG LEVEL MEASUREMENTS AFTER HIGH DOSE METHOTREXATE INFUSION FOR TREATMENT PLANNING IN PEDIATRIC LEUKEMIA

Abstract

Introduction: Although high-dose Methotrexate (MTX) is a successful chemotherapeutic agent used in the treatment of acute lymphoblastic leukemia in childhood, life-threatening toxic effects are rarely seen. Therefore, frequent follow-up of drug levels is recommended. The study researched the necessity of drug level measurement and a minimum safe number of measurements.

Materials and Methods: The files of pediatric patients with Acute Lymphoblastic Leukemia receiving high-dose MTX treatment in a single center between 2018 and 2021 were retrospectively reviewed. The treatment protocol was: 3000 mL/m² alkaline hydration fluid was continued until the 72^nd hour together with 2 gr/m² continuous MTX infusion in the low-risk group and 5 gr/m² in moderate and high-risk groups, and 15 mg/m²/dose folinic acid was given at the 42^nd, 48^thand 54^th hours.

Findings: 456 MTX treatments were evaluated in 114 patients. Similar results (p>0.05) were obtained in the MTX level measurements performed at the 24^th, 42^nd, 48^th, and 54^th hours after MTX administration. In the repeated measurements, the data at the 42^nd hour were similar (p=0.021). The number of cases that were >150 mmol/L at the 24^th hour of methotrexate infusion and above 1 mmol/L at the 42^nd, 48^th, and 52^nd hours were found to be similar in the repeated measurements. Conclusion: Although recommended, frequent follow-up of MTX levels might not always indicate toxicity. In centers with limited laboratory facilities, the MTX level measured at the 42^nd hour in the first treatment might be a practical approach to guide the management of other MTX treatments.