Impact of proton versus photon radiotherapy on overall survival in the management of spinal chordoma and mortality risk prediction: a nationwide analysis.

PURPOSE: This study aims to provide a national-level insight into the optimal management of spinal chordoma, a type of rare and complicated malignancy, and to identify effective radiation therapy (RT) strategies for patients with spinal chordoma by comparing photon versus proton therapies.

METHODS

Patients with histologically confirmed spinal chordoma were identified from the NCDB. Patients' demographics, disease characteristics and treatments were compared between the radiation and no-radiation groups. Kaplan-Meier assessed 10-year overall survival (OS). Multivariate Cox regression and machine learning models-Random Survival Forest and Gradient Boosting-identified predictive factors and thresholds of tumor size for mortality risk, with SHAP used to quantify predictor importance.

RESULTS

Of 1204 patients, 495 (41.1%) received RT; 73.9% received photons and 26.1% protons. GTR significantly improved OS compared to STR (p < 0.0001). RT was associated with reduced short-term morality at 90-days (p = 0.025) and 1-year (p = 0.016). Proton therapy showed superior 10-year OS compared to photon therapy (p = 0.019). Beam technology, BED dose, sequence, and reirradiation had minimal impact on OS. Cox regression identified age (HR = 1.03, p < 0.001), STR (HR = 1.42, p = 0.005), and proton therapy (HR = 0.58, p = 0.044) as independent mortality predictors. Machine learning identified tumor size thresholds (photons: 83 mm; protons: 70 mm) and ranked age, tumor size, and EOR as top survival predictors.

CONCLUSION

Aggressive surgical resection (GTR) remains the primary treatment for spinal chordoma. Proton therapy that allows for dose escalation provided 10-year survival benefits compared to photon therapy. Age, tumor size and EOR are important factors in predicting 10-year mortality risk.