Dose-individualization Efficiently Maintains Sufficient Exposure to Methotrexate without Additional Toxicity in High-dose Methotrexate Regimens for Pediatric Acute Lymphoblastic Leukemia

Objective Methotrexate (MTX) can be safely administered to most patients but may cause severe toxicity in others. This study aimed to summarize the characteristics of high-dose methotrexate (HD-MTX) chemotherapy and to evaluate whether the modified dose-adjustment program was able to improve the maintenance of sufficient MTX exposure levels while minimizing toxicities. Methods We evaluated 1172 cycles of high-dose MTX chemotherapy from 294 patients who were treated according to the CCCG-ALL-2015 protocol (clinical trial number: ChiCTR-IPR-14005706) and analyzed the data of actual MTX dosage, MTX concentration, toxicity, and prognosis. We compared data between the dose-adjustment Program 1 (fixed 20% reduction in dose) and the dose-adjustment Program 2 (dose-individualization based on reassessment of the creatine clearance rate and the MTX concentration-monitoring point at 16 h), which were applied if the MTX clearance was delayed in the previous cycle. Results The patients who used Program 2 had higher actual MTX infusion doses and infusion rates and were able to better maintain the MTX concentration at 44 h at the established target value than those on Program 1 (P<0.001). No significant differences in toxicities were found between these two programs except that abnormal serum potassium levels and prolonged myelosuppression in intermediate-risk/high-risk patients were more frequently observed in patients using Program 2 (P<0.001). No significant correlations were observed between the MTX dose, dose-adjustment programs, or MTX concentrations and relapse-free survival. Conclusion Adjusting the MTX dose using Program 2 is more efficient for maintaining sufficient MTX exposure without significantly increasing the toxicity.