Neutron Radiotherapy: Oral Complications and Recurrences of Salivary Gland Malignancies

Objectives: The literature regarding oral complications following neutron beam radiation therapy (NRT) is limited. A previous study conducted by the University of Washington reviewed NRT indications, dosing, prognosis, and oral complications of NRT for oral salivary gland malignancies. However, this previous study did not analyze any malignancies in the parotid or base of tongue. The objective of this follow up study was to estimate: 1) the rates of local-regional control and 2) the frequency of oral complications from NRT for all head and neck salivary gland malignancies.
Methods: This is a retrospective case series of patients with salivary gland malignancies treated with NRT by the Radiation Oncology Department at the University of Washington from 1997 to 2010. Variables included patient demographics, tumor staging and characteristics, operative and pathological findings, dosing, and complications. Data were extracted from patient charts and by telephone for follow-up and quality-of-life information. Univariate statistics were computed for each study variable and Kaplan-Meier methods were used to estimate local-regional recurrence.
Results: The sample was composed of 562 patients (48% male and 52% female) with a mean age of 54.1 years (± 15.9). Adenoid cystic carcinoma (47.1%) and parotid gland location (55.8%) predominated. Perineural and lymphatic invasion was present in 49% and 26% of subjects, respectively. The 6-year locoregional control rate was 70%. Mucositis and xerostomia occurred in approximately 81% and 83% of patients, respectively. Osteoradionecrosis (ORN) occurred in 5.1% of patients.
Conclusions: The results show that the locoregional control rate for NRT patients compares favorably to that reported in the literature for photon radiation treatment of the same areas. The frequency of ORN was comparable to photon radiation treatment of the same areas (4-7%). Given the potential benefits of NRT on salivary gland malignancies, dental professionals should be educated regarding its indications and oral complications.