A Prospective, Self-Controlled and Randomized Study about the Optimal Timing of Leucovorin Rescue after High Dose Methotrexate Management

Background and objectives: Methotrexate (MTX) is a folic acid reductase inhibitor widely used. Peripheral infusion of high dose MTX (HD-MTX) could prevent the central nervous system recurrence of leukemia and NHL. Due to the blood brain barrier, only 1-3% of MTX in the peripheral blood can enter the cerebrospinal fluid. Improving the peripheral MTX drug dosage helps to improve MTX concentration in the cerebrospinal fluid. However, high concentration of MTX has serious side effects to normal organs. Leucovorin (CF) rescue is given to reduce the toxic effect of methotrexate on normal cells. During high dose MTX therapy, monitoring of serum concentration of MTX and timely CF rescue therapy are mandatory so as to maximum the efficacy of MTX and minimize the toxicities. Due to the lack of randomized clinical trials with large sample, the safe dose and most appropriate time of leucovorin rescue treatment are of no consensus. In order to study the effect of different time of leucovorin rescue treatment on the serum concentration of MTX, we carried out this study.

Patients and methods: We included patients who had pathological diagnosis of non-Hodgkin's lymphoma and indications to receive HD-MTX as single agent or component in combined regimen consecutively from October 2011 to June 2014 at our hospital. Patients were randomized to receive CF rescue at the sixth hour after MTX infusion in the first course and twelfth hour in the second course or the twelfth hour in the first course and sixth hour in the second course. A dosage of 3.5 g/m² of MTX was provided. Adequate hydration, alkalization and monitoring of laboratory tests were administered. Intrathecal injection of MTX plus cytarabine and dexamethasone were given after MTX infusion. 100mg of CF was given at the first time, then 30mg of CF were given every 6 hours for a total of 7 times until the plasma concentration of MTX were lower than 1×10^-7mol/L. Blood samples were collected at 2, 12, 18, 24, 28, 72 hours after the beginning of MTX infusion. High performance liquid chromatography was used to test the plasma concentration of MTX.

Results: There were 23 male patients and 12 female patients with a mean age of 41 years. Most of patients were diagnosed as diffuse large B cell lymphoma (65.7%). Eleven cases (31.4%) had central nervous system invasion at the time of HD-MTX treatment. Twenty-one patients (51%) had more than one extra-nodal lesion. Sixteen patients were randomly to be rescued at the sixth hour in the first course then the twelfth hour in the second course. Nineteen patients were randomly to be rescued at the twelfth hour in the first course then the sixth hour in the second course. The plasma concentration of MTX of patients rescued at the sixth hour at the time of 2，12，18，24，48 hours were 5.21±0.36×10^-5mol/L，8.01±0.635×10^-5mol/L，4.57±1.67×10^-6mol/L，1.43±0.83×10^-6mol/L，0.1±0.1×10^-6mol/L, respectively；The plasma concentration MTX of patients rescued at the twelfth hour at the time of 2，12，18，24，48 hours were 5.46±0.34×10^-5mol/L，8.65±0.663×10^-5mol/L，5.4±0.93×10^-6mol/L，1.12±0.21×10^-6mol/L，0.1±0.24×10^-6mol/L, respectively. There was no significant difference of MTX concentration level between patients treated with different CF rescue timing, P＞0.05. Most of patients achieved maximal MTX concentration at the twelfth hour, and descended to be lower than the minimal effective concentration at the eighteenth hour. At the forty-eighth hour, majority of patients had MTX concentration being in a safe range. The rate of grade 3 to 4 adverse reactions including neutropenia, anemia, thrombocytopenia and grade 1 to 2 side effects including neutropenia, thrombocytopenia, mucositis, fatigue, and MTX discharge delay were higher when patients were rescued with CF at the twelfth hour, though P＞0.05.

Conclusion: Most of patients treated with high dose MTX reached the maximum MTX concentration at the twelfth hour after MTX infusion, and descended to be under the minimal effective concentration at the eighteenth hour, then to be in the safe range at the forty eighth hour. No significant difference of MTX concentration was found between patients rescued with CF at the sixth hour or the twelfth hour. However, adverse reactions were lower when patients were treated with CF rescue at the sixth hour. It seems a better choice to give patients CF rescue at the sixth hour after MTX infusion.