Relationship of serum methotrexate concentration in high-dose methotrexate chemotherapy to prognosis and tolerability: A prospective cohort study in chinese adults with osteosarcoma

BACKGROUND: Cancer that originates in the bone, termed primary bone cancer, is rare. Osteosarcoma (OS) occurs primarily in growing bone tissue and is more prevalent in children and adolescents. OS in adults is rare, with 3 to 5 cases per million population per year worldwide. There are limited data on treatment-related prognosis and adverse reactions in adults reported in the literature. OBJECTIVES: The aims of this study were to investigate factors that influence serum methotrexate (MTX) concentrations used in chemotherapy in Chinese adult patients with OS, and to determine the correlations (based on age, sex, and dosage), if any, between MTX and prognosis, in terms of disease-free survival (DFS) and overall survival (OAS), and tolerability. METHODS: Adult patients aged ≥30 years with OS received ≥3 courses (2 courses before surgery and 3-4 courses postsurgery) of high-dose MTX (6 or 8 g/m(2)) combined chemotherapy. The regimen consisted of day 1: MTX + folinic acid (herein referred to as citrovorum factor rescue); day 8: cisplatin; days 21 to 25: ifosfamide + mesna; and day 21: doxorubicin. Serum MTX concentrations were assessed immediately after the end of infusion (baseline) and at 24 and 48 hours using high-performance liquid chromatography. Changes in serum MTX concentrations, factors that influence serum MTX concentrations, and the relationship between serum MTX concentrations and prognosis and tolerability (determined by adverse reactions) were analyzed. Patients received a second course of treatment after a 3-week period. RESULTS: Ninety patients (58 men, 32 women; age range, 30-67 years) with OS were included in the study. A total of 532 courses of combined chemotherapy were administered. The serum MTX concentrations ranged widely at baseline (244.31-929.68 mol/L, Cmin and Cmax, respectively) and at 24 hours (0.73-28.24 mol/L, respectively), suggesting that the serum MTX concentrations varied significantly between different individuals and within the same individual at different time points. The serum MTX concentrations in ~23% of cases (122/532) determined at 24 and/or 48 hours were numerically higher than the safety values (according to Nirenberg's reference: irreversible damage if MTX concentration was >10 umol/L and > 1 umol/L at 24 and 48 hours, respectively). No correlation was found between high serum MTX concentration at baseline and high serum MTX concentration at 24 hours (r = 0.401). The prevalences of the 3 most common adverse reactions in these patients were depressed white blood cell count (44.03%), dental ulcer (23.0%), and rash (18.0%). However, in the remaining 410 courses in which serum MTX concentrations were lower than the safety values, these prevalences were 14.6%, 3-9%, and 2.4%, respectively. Neither age nor sex was significantly associated with MTX Cmax, but dosage was (P < 0.05). Patients with a serum MTX Cmax concentration >500 μmol/L at baseline had a significantly longer DFS rate than those with ≤500 umol/L (P = 0.040). There were no significant between-group differences in the OAS rates. conclusions: In these Chinese patients with OS, serum MTX concentrations measured at different time points were varied. The findings suggest that adverse reactions occurred in patients whose serum MTX concentrations at 24 and/or 48 hours were higher than the safety values. The dosage appeared to have influenced MTX Cmax, while sex and age did not, and the Cmax was significantly related to DFS but not OAS.