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

## TL;DR

This study compares proton and photon radiotherapy for spinal chondrosarcoma, finding that proton therapy and high-dose radiation improve survival, especially when combined with surgery.

## Contribution

The study introduces a nationwide analysis of proton vs. photon therapy for spinal chondrosarcoma and identifies tumor size thresholds and predictive models for mortality risk.

## Key findings

- Proton therapy showed superior survival outcomes compared to photon therapy in spinal chondrosarcoma patients.
- High-dose radiation (BED >70 Gy) and SBRT improved survival when combined with surgery.
- Machine learning identified tumor size thresholds and prognostic factors for 10-year survival.

## Abstract

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.

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.

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 identified 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.

Gross total resection (GTR) is the most effective treatment for spinal chondrosarcoma. High-dose radiation 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.