Treatment Patterns and Survival Outcomes in High-Grade Osteosarcoma: A Multicenter Retrospective Study

This is a multicenter, medical-record-based, retrospective observational study of approximately 400 patients with high-grade osteosarcoma treated at four sites in the Republic of Korea. The study describes treatment patterns and survival outcomes (event-free survival \[EFS\], progression-free survival \[PFS\], and overall survival \[OS\]) in patients who completed or discontinued first-line treatment for high-grade osteosarcoma, irrespective of complete remission status. The primary objective is to retrospectively estimate the 12-month EFS rate, calculated from the date of diagnosis, in the full cohort of high-grade osteosarcoma patients. Key secondary objectives evaluate EFS and OS from the date of confirmed complete remission/no evidence of disease (CR/NED) in the subset of clinically high-risk patients who achieve CR/NED, in order to establish a historical reference data supporting the design and interpretation of a future prospective clinical trial of vactosertib as maintenance therapy.