4CPS-281 High dose methotrexate in paediatric osteosarcoma patients: effectiveness and safety

Background and importance Osteosarcoma is the most frequent bone tumour, and is more prevalent in paediatric patients. Treatment of osteosarcoma in paediatric patients includes administration of methotrexate at high doses, which allows the drug to penetrate the bone tissue in adequate concentrations. Serum peak methotrexate levels between 1000 and 1500 µM have been correlated with efficacy. Aim and objectives The objective of this study was to evaluate the effectiveness and safety of methotrexate 12 g/m2 as treatment for osteosarcoma in paediatric patients. Material and methods This was an observational retrospective study including paediatric osteosarcoma patients treated with 12 g/m2 methotrexate infusion from January 2014 to June 2020. Data were extracted from the patients’ clinical history. Peak methotrexate serum levels were extracted immediately after the 4 hour infusion. Variables collected were: age, sex, number of cycles received, peak methotrexate serum levels and adverse events associated with the methotrexate infusion during hospitalisation. Results 25 patients, 56% (14) males, median age 14 (4–17) years, received 159 cycles of methotrexate. The median number of cycles per patient was 8 (2–8). Median peak methotrexate serum levels were 1280 (280–2980) µM; 74.84% of peak serum levels were >1000 µM. Conclusion and relevance When comparing our results with published studies, we found that the patients included in our study achieved effective concentrations of methotrexate at a higher percentage (75% vs 63%)1 with severe adverse events being less frequent (9% vs 39%).2 According to these results, methotrexate infusion was effective and safe in the studied population. References and/or acknowledgements Zelcer S, Kellick M, Wexler LH, et al. Methotrexate levels and outcome in osteosarcoma. Pediatr Blood Cancer 2005;44:638–642. Villegas Rubio JA, Cacciavillano W, Rose A, et al. Ambulatory high-dose methotrexate administration in paediatric osteosarcoma patients at a single institution in Argentina. J Pediatr Hematol Oncol 2017;39:e349–e352. Conflict of interest No conflict of interest