A Prospective Evaluation of Acute Toxicity from Proton Therapy for Targets of the Parotid Region

Mucosal toxicities are common acute effects from head-and-neck radiotherapy. The parotid region is ideal for proton therapy (PT) due to sparing radiosensitive tissues distal to the target. We prospectively evaluated acute mucosal toxicity in patients treated with PT for parotid cancers.

Twenty-three patients received primary (n=7) or adjuvant (n=16) PT for parotid cancers, including salivary gland carcinoma (n=17), skin carcinoma with perineural invasion (n=5), and Ewing sarcoma (n=1). PT consisted of 2-3 passively scattered fields. Median dose was 70 Gy (RBE) (range, 55.8-74.4) using various fractionation schedules. Seven patients received concurrent chemotherapy. Acute toxicities, nutritional status, and weight were prospectively evaluated weekly.

Most patients experienced no or minimal toxicity throughout therapy. There were no grade 4 toxicities and only 1 transient grade 3 dysphagia. At the end of treatment, the worst mucositis was grade 2 in 35% with 43% experiencing no mucositis; the worst dysphagia was grade 2 in 26 % with 48% having no dysphagia; the worst dysgeusia was grade 2 in 23% with 50% experiencing no dysgeusia; and the worst xerostomia was grade 2 in 14% with 23% experiencing no xerostomia. The median weight loss was 3%. No patient required a feeding tube or intermittent intravenous hydration.

PT for tumors of the parotid region results in very low rates of mucosal toxicity. Nutritional status and weight were preserved throughout therapy. These results should be validated with patient-reported outcomes, and their impact on functional recovery and treatment costs remain unexplored.