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evidence of disease (CR/NED) in the subset of clinically high-risk patients who achieve CR/NED, in order to establish a historical reference data supporting the design and interpretation of a future prospective clinical trial of vactosertib as maintenance therapy.

Inclusion Criteria: * Pathologically diagnosed high-grade osteosarcoma; age ≥12 years. * First-line treatment for high-grade osteosarcoma completed or ended at the study institution on or before 2021-06-30. * Core data required for survival endpoint assessment (EFS, PFS, OS) are available, with at least one of the following satisfied: (a) at least 12 months of follow-up from the date of diagnosis; or (b) an event (relapse, metastasis, disease progression, or death from any cause) confirmed within 12 months of diagnosis. Exclusion Criteria: * Primary tumor of soft-tissue origin rather than bone, confirmed pathologically. * History of a malignancy other than primary osteosarcoma, unless clinically insignificant and fully treated prior to osteosarcoma diagnosis with no investigator-judged impact on osteosarcoma treatment course or survival analysis. * Core data required for survival analysis cannot be verified. * Transferred to another institution with no available follow-up information, where neither event occurrence, last follow-up date, nor survival status can be determined from pre-transfer records. * Investigator-judged data errors or inconsistencies