Relationship of peak serum methotrexate concentration to prognosis and drug tolerance in non-metastatic extremity osteosarcomas.

Abstract

This study aimed to explore whether peak serum methotrexate concentration (Cmax) correlated with adverse events, overall survival (OS) and event-free survival (EFS) in patients with primary extremity osteosarcoma. Patients with extremity osteosarcoma who were treated at our center between 2005 and 2015 were retrospectively studied. All the patients were Enneking stage II and had received standard perioperative chemotherapy composed of high-dose methotrexate, doxorubicin, cisplatin and ifosfamide. Cmax and treatment-associated toxicities of each cycle were recorded. OS and EFS were estimated and compared by Kaplan-Meier survival analysis, and Cox regression models were performed for univariate comparisons. In total, 567 patients were followed for an average of 53months (24-104months). The estimated 3- and 5-year EFS were 71.7 and 63.1%, and the 3- and 5-year OS were 78.2 and 72.9%, respectively. Cmax ranged from 527 to 2495µmol/L with a mean value of 931 ± 106µmol/L. No significant differences in EFS and OS (p = 0.18 and p = 0.28) were observed among patients with a mean Cmax > 1500, > 1000, > 700 and < 700µmol/L. However, patients with a mean Cmax > 1500µmol/L had significantly increased rates of grade 3-5 toxicity. In the univariate analysis, Cmax was not a prognostic factor for EFS (p = 0.08) or OS (p = 0.16). Cmax did not correlate significantly with the oncologic prognosis of non-metastatic extremity osteosarcoma patients treated by multi-agent chemotherapy; however, Cmax correlated closely with toxicities and complications. The persistent inclusion of methotrexate in classical multidisciplinary chemotherapy was questioned and should be examined in future trials.