A Competing Risk Nomogram for Predicting Outcomes in Older Patients with Chondrosarcoma: Insights from the SEER Database

Objective Chondrosarcoma is a common malignant bone tumor in older adults with limited research on survival outcomes in this population. This study aims to devise and validate a nomogram for predicting overall survival (OS) and cancer-specific survival (CSS) in older chondrosarcoma patients. Methods A retrospective analysis of older chondrosarcoma patients (2004–2018) from the SEER database was conducted. Cox regression identified risk factors to build nomograms for 1-, 2-, and 3-year OS and CSS. Model performance was assessed by C-index, ROC curves, AUC, calibration curves, and decision curve analysis. Kaplan-Meier and log-rank tests evaluated OS risk stratification. Results The study included 676 older chondrosarcoma patients, randomly divided into a training group (n = 475) and validation group (n = 201). The OS nomogram incorporated eight variables: surgery, M stage, tumor size, grade, histologic type, primary tumor site, sex, and age, while the CSS nomogram included seven factors, excluding tumor size. In the training group, the OS nomogram achieved a C-index of 0.785 (95% CI: 0.756–0.814), and 0.810 (95% CI: 0.767–0.853) in the validation group. For CSS, C-indices at 1, 2, and 3 years were 86.4, 84.0, and 81.5 in the training group, and 91.0, 89.7, and 89.9 in the validation group. The nomograms demonstrated strong calibration and clinical utility, outperforming TNM staging in stratifying patients by risk and improving predictive accuracy. Decision curve analysis further confirmed their value in clinical decision-making. Conclusion This study established a nomogram for older chondrosarcoma patients. Future studies should refine models with updated prognostic factors to enhance patient management.