The CATSINDO Trial - Clinical and Translational Study in Newly Diagnosed Osteosarcoma

This Phase II, multi-institutional study evaluates the safety of hospital discharge at higher serum methotrexate (MTX) levels in children, adolescents, and young adults with newly diagnosed high-grade osteosarcoma receiving standard-of-care high-dose methotrexate (HD-MTX) as part of MAP chemotherapy. Participants are discharged once they meet the pre-defined MTX clearance, kidney function, and clinical safety criteria. Methotrexate discharge thresholds are evaluated using an adaptive Bayesian threshold-finding design, starting at a serum MTX level of less than or equal to 0.15 micromolar, with possible escalation or de-escalation based on observed toxicity. Secondary objectives include comparison of hospital length of stay and estimated inpatient costs with historical controls using traditional discharge criteria. Optional correlative studies include patient-derived osteosarcoma tumor organoids and circulating tumor cells to evaluate chemotherapy sensitivity and other future research. A separate retrospective chart review of prior patients treated with HD-MTX is included to understand safety outcomes and MTX clearance patterns.