Abstract: Background: There is controversy at home and abroad as to whether delayed high-dose methotrexate (MTX) excretion should be rescued by hemodialysis. Objective: To investigate the effectiveness of high-flux hemodialysis (HF-HD) on MTX clearance in children with tumors. Design: Case series report. Methods: A retrospective analysis was performed for consecutive cases with blood levels >10 μmol·L-1 at 44 h after MTX chemotherapy at the Department of Hematology Oncology at Shanghai Children's Medical Center affiliated with Shanghai Jiao Tong University School of Medicine between January 2016 to June 2021. The children with calcium folinate (CF) alone were in the non-HF-HD group, and those with HF-HD + CF were in the HF-HD group. Gastrointestinal tracts, liver and kidney function as well as hematologic toxicity indicators were compared between the two groups. Main outcome measures: The incidence of adverse reactions to liver and kidney function. Results: There were 20 times delayed MTX excretion with 9 in the non-HF-HD group and 11 in the HF-HD group. According to Common Terminology Criteria for Adverse Events v4.0, there was no significant difference in creatinine, uric acid, ALT, AST, mucositis, 24 h MTX concentration, and the time required for MTX concentration to return to normal between the CF group and the HF-HD group. There was no significant difference in the incidence of hematologic adverse events between the two groups, while the differences in incidences of abnormalities of AST, ALT, fever, mucositis, WBC, NE, Hb, and PLT were not statistically significant between the two groups. Conclusions: If the kidney function is normal, CF rescue can be used for children with tumors to clear MTX effectively and safely, and dialysis is not recommended unless it is necessary.

Key words: Methotrexate, Plasma Concentration, Calcium folinate, High-flux hemodialysis, Rescue