Pelvic Osteosarcoma: Outcomes of Surgically Treated Patients in a Retrospective Single-Center Study

(1) Background: Pelvic osteosarcoma accounts for a small proportion of osteosarcoma cases but is associated with significantly poorer outcomes than extremity tumors. This study evaluates contemporary survival outcomes and prognostic factors in a single-center cohort. (2) Methods: We retrospectively analyzed 56 patients with primary pelvic osteosarcoma treated between 2006 and 2019. Demographic characteristics, surgical margins, adjuvant therapies, local recurrence, metastasis, survival outcomes and the Musculoskeletal Tumor Society (MSTS) Score were assessed. Kaplan-Meier analysis was performed for overall survival (OS), including subgroup analyses by age and Enneking classification. (3) Results: Median age at surgery was 24 years. R0 margins were achieved in 96.4% of cases. OS at 1, 3, and 5 years was 69%, 54%, and 48%, respectively. Younger patients (≤25 years) showed significantly improved 5-year OS (68%) compared with older groups. Enneking classification showed limited prognostic discrimination. Metastatic disease at any time strongly predicted inferior survival (5-year OS 30% vs. 66%). The mean MSTS score one year after operation was 14.1 points. Functional outcome showed marked variability and was strongly influenced by patient age, extent of resection, reconstruction strategy, and postoperative complications. Younger patients and those undergoing limited or non-acetabular reconstructions achieved superior functional results, whereas complex endoprosthetic reconstructions and revision-requiring complications were associated with reduced MSTS scores. (4) Conclusions: Pelvic osteosarcoma continues to be associated with substantial morbidity and mortality. Younger age and absence of metastatic disease are strong predictors of improved survival. Functional outcomes are typically moderate; further advances are needed to improve results.