The effect of postoperative chemotherapy on survival outcomes and a nomogram for predicting overall survival in chondroblastic osteosarcoma.

The analysis of chondroblastic osteosarcoma (CBO) was conducted using data from the Surveillance, Epidemiology, and End Results (SEER) database (2000-2019).​ A cohort of 317 surgically treated CBO patients was analyzed, with 261 (82.3%) receiving adjuvant chemotherapy and 56 (17.7%) classified as no/unknown chemotherapy recipients. The median diagnosis year of CBO patients was 2005 and the median follow-up time was 5.25 years (63 months).​​ Kaplan-Meier analysis demonstrated that chemotherapy significantly improved overall survival (OS) (P = 0.011), a finding corroborated after propensity score matching (P = 0.036). Specifically, the 5-year, 10-year, and 15-year overall survival(OS) of patients who received chemotherapy were 52.11%, 35.25%, and 25.29%, respectively. In contrast, the corresponding survival rates of patients who did not receive chemotherapy or whose chemotherapy status was unknown were 48.21%, 39.29%, and 25.00%, respectively. Subgroup analyses revealed enhanced chemotherapy efficacy in males (HR = 0.48, P = 0.01), high grade tumors (HR = 0.54, P = 0.015), and high income patients (HR = 0.35, P = 0.001), while ​stage stratified analysis showed that the overall survival benefit of chemotherapy was limited to patients with stage I-II disease (P for interaction = 0.008). Further interaction analysis revealed that the survival benefit of chemotherapy in patients with stage III-IV disease was significantly attenuated compared to those with stage I-II disease (HR = 0.06, P = 0.049), indicating a pronounced stage dependent effect. Multivariate Cox regression identified age, tumour stage and radiotherapy as independent prognostic factors. The constructed nomogram integrating these factors with marital status and chemotherapy achieved C-indices of 0.674 (training set) and 0.691 (validation set). Notably, it exhibited strong discriminative ability with AUC values of 0.672, 0.658, and 0.657 for predicting 5-, 10-, and 15-year OS in the training set, and even higher values of 0.741, 0.712, and 0.745 in the validation set. This tool provides individualized 5-, 10-, and 15-year OS predictions, addressing critical gaps in CBO specific prognostic assessment and supporting personalized therapeutic decision making.