摘要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.