Carbon ion radiotherapy as an initial treatment for patients with carcinoma of the parotid gland

The mainstay of treatment for carcinoma of the parotid gland is surgical removal, which is often performed in conjunction with postoperative radiation therapy when the tumor has a high grade of malignancy or positive surgical margins. Carbon ion radiotherapy (C-ion RT) offers more precise dose localization in the target lesion and has a greater biological effect on malignant tumors than conventional X-ray therapy. Here, we evaluated the efficacy of C-ion RT against carcinomas of the parotid gland and compared C-ion RT to curative surgery in terms of survivals and adverse events. Clinical data from patients with carcinomas of the parotid gland who were treated at Gunma University Hospital between August 2011 and August 2016 in were retrospectively analyzed. Progression-free survival (PFS) and overall survival (OS) were examined between the surgery and C-ion RT groups. Adverse events including facial nerve palsy were also evaluated. This study enrolled 33 patients with carcinoma of the parotid. Eleven patients were treated with C-ion RT, whereas 22 patients were underwent surgery. No significant difference in the PFS (p = 0.147) or OS (p = 0.580) was observed between the two groups. Radiation dermatitis, otitis externa, otitis media, and radiation brain necrosis were found in 11 patients (100%), 9 patients (81.8%), 5 patients (45.5%), and 1 patient (9.1%) treated with C-ion RT, respectively. Interestingly, 3 of the 4 patients with facial nerve palsy showed a partial improvement after treatment with C-ion RT. Our results revealed that C-ion RT could be a promising treatment modality in patients with locally advanced and/or inoperable diseases.