Proton beam therapy reduces dose to at-risk organs in locally advanced head and neck tumours

Patients with locally advanced head and neck tumours who underwent proton beam therapy (PBT) experience significant decreases in dose to organs at risk (OAR) while maintaining comparable target coverage relative to volumetric modulated arc therapy (VMAT) treatment plans, reports a study.

“Locally advanced tumours of the head and neck region often lie in close proximity to critical OARs,” the authors said. “Providing effective treatment coverage to these malignancies while minimizing radiation dose to surrounding OARs is advantageous.”

Patients with locally advanced head and neck tumours treated with PBT at the University Hospitals Seidman Cancer Center in Ohio, US, from 2016 to 2019 were identified and included in this study.

The authors assessed outcomes including mean and maximum doses for the OAR structures for each treatment plan, overall survival, time to local-regional or distant progression, and presence of acute and late toxicities. They also compared mean and maximum doses to OAR structures between treatment modalities using a paired Wilcoxon signed-rank test.

Forty-two patients were included in the analysis. Clinical target volume coverage was >95 percent for both PBT and VMAT treatment plans.

Over a median follow-up of 27 months, PBT plans resulted in a substantial decrease to the mean doses of all OARs, as well as max doses to most OARs (p<0.05). The largest mean dose reduction was observed in the contralateral cochlea (71 percent) and parotid glands (75 percent).

At 4 years, overall survival was 44.75 percent. At 2 years, freedom from local-regional progression stood at 73.28 percent. Of note, most patients developed Common Terminology Criteria for Adverse Events grade I dermatitis, mucositis, or both.

“Further refinements to proton therapy may have the potential to further minimize dose to critical structures,” the authors said.