Impact of proton vs. photon radiotherapy on overall survival in the management of spinal chondrosarcoma and mortality risk prediction: A nationwide analysis

Background. Spinal chondrosarcomas are rare, aggressive bone tumors with limited data on optimal radiotherapy strategies, particularly regarding the comparison between proton and photon therapies. This study aims to evaluate long-term survival outcomes and identify effective treatments and risk factors using the National Cancer Database. Methods. Patients diagnosed with spinal chondrosarcomas were categorized into radiation and no-radiation groups. The radiation group was subdivided into proton and photon therapy cohorts. Univariate and Kaplan–Meier analyses assessed demographic, clinical, and survival outcomes. Multivariate Cox proportional hazards models identified prognostic factors, and survival predictive models were evaluated using Area Under the Curve (AUC) metrics. Results. Of 1971 patients, 343 (17.4%) received radiation. Surgery was less common in the radiation group (53.9% vs 82.6%, P < .001). Combined surgery and radiation had the best survival outcomes, with proton therapy showing superior survival to photons (P < .001). High-dose radiation (Biologically Effective Dose [BED] >70 Gy) and Stereotactic Body Radiation Therapy (SBRT) improved survival (P < .001). Surgery was associated with increased mortality risk (hazard ratio [HR] = 0.35, P < .001), while radiation showed increased risk (HR = 1.31, P = .003). Machine learning iden tified tumor size thresholds of 75 mm for photon and 70 mm for proton therapy as predictive of mortality. DeepSurv (AUC = 0.708) identified distant metastasis, tumor size, and age as important prognostic factors for 10-year survival. Conclusion. Gross total resection (GTR) is the most effective treatment for spinal chondrosarcoma. High-dose radi ation therapy (BED > 70 Gy) can be combined with surgery to improve survival in advanced cases. Proton therapy offers superior long-term survival compared to photons, and dose-escalated techniques (Stereotactic Radiosurgery [SRS] and Intensity-modulated radiation therapy [IMRT]) show potential in enhancing outcomes.