Combining clinical and dosimetric features in a PBS proton therapy cohort to develop a NTCP model for radiation-induced optic neuropathy.

PURPOSE

Radiation-induced optic neuropathy (RION) is a rare, yet severe complication following radiation therapy for brain, head and neck or skull-base tumors. While several risk factors such as age, metabolic syndrome and delivered dose have been identified, we aimed at expanding the understanding of the mechanisms of interplay regarding dosimetry and patient variables leading to the onset of RION with a focus on proton therapy.

METHODS AND MATERIALS

In this retrospective study we have investigated proton-specific risk factors by comparing common phenomenological NTCP models with a multivariate analysis that includes clinical features on a cohort of skull-base and head and neck cancer patients treated with pencil beam scanning (PBS).

RESULTS

Although predictive power of the Lyman-Kutcher-Burman and Poisson models was limited for this dataset, the addition of clinical variables such as age, tumor involvement, hypertension or gender remarkably increased model performance.

CONCLUSION

Based on our assessment, the maximum dose in the optical apparatus is confirmed the most intuitive risk factor. However, above a certain dose threshold, clinical patient characteristics are the deciding factors for the onset of RION. Interestingly, we observed a tendency towards a volume effect that, if confirmed, would imply a benefit for high precision radiotherapy techniques such as proton therapy for the treatment of patients with high clinical risk for RION.