Real World Data from Patients With Osteosarcoma Treated in 8 Medical Centers in Greece: Ninety Percent or Greater Tumor Necrosis Is Associated With Disease-free Survival.

Background/Aim: Advanced osteosarcomas tend to have poor prognosis with limited therapeutic options beyond first-line therapy. This retrospective, multi-institutional study aimed to evaluate the association between histological response to chemotherapy and survival outcomes, as well as the influence of sex, tumor size, location, and other factors in a Greek cohort. Patients and Methods: We retrospectively studied the predictive value of distant metastasis, percentage of necrosis, and grade of tumor in 77 cases of sarcoma treated in 8 medical centers in Greece between 2004 and 2022. Median follow up time from the time of diagnosis was 27 months. Statistical analysis was performed using a two-sided significance level of Results: Our analysis revealed that short bones were affected significantly more frequently in older [median age=43 years, interquartile range (IQR)=30-50] than younger patients (median age=26 years, IQR=18-40). Distant metastasis was significantly associated with shorter overall survival [OS; HR=3.7, 95% confidence interval (CI)=1.5-9.16, Conclusion: Osteosarcoma patients with 90% or more tumor necrosis were found to have survival advantage. Differences in DFS between sexes highlight the need for tailored treatment approaches and further exploration of biological underpinnings.