A Multicenter Study of Carbon-Ion Radiation Therapy for Head and Neck Adenocarcinoma

Head and neck (HN) adenocarcinoma is rare, and to date, there have been no reports of prospective studies. We retrospectively evaluated the efficacy and safety of carbon-ion radiation therapy (C-ion RT) for HN adenocarcinoma in institutions in Japan.

HN adenocarcinoma patients with N0M0 or N1M0 disease who were treated with C-ion RT at institutions in Japan between November 2003 and December 2014 were analyzed retrospectively. We enrolled 47 patients (30 male and 17 female patients; median age, 60 years) with HN adenocarcinoma.

Primary sites included the nasal and paranasal sinus in 21 patients, orbit in 11, salivary grand in 7, oral cavity and pharynx in 6, and acoustic organ in 2. Thirty-two patients had T4 tumors, 6 had T3, and 6 had T2. Forty-five patients received a diagnosis of N0 disease, whereas 2 had N1 disease. The median total dose of C-ion RT and the number of fractions were 64.0 Gy (relative biological effectiveness) and 16 fractions, respectively. The median follow-up period was 51 months (range, 6-118 months). The 2- and 5-year overall survival rates were 87.9% and 60.4%, respectively, and the 2- and 5-year local control rates were 83.3% and 79.3%, respectively. Multivariate analysis showed that operability (patients with operable tumors) (P=.045) and fractionation (16 fractions) (P=.010) were significant independent prognostic factors for better overall survival. No grade 5 late morbidities were observed. Grade 4 late morbidities were observed in 4 patients, and all of these grade 4 morbidities were visual impairments. All 4 patients with grade 4 visual impairment had T4 tumors in the nasopharynx or paranasal sinuses, which implied inoperable tumors with orbital or brain invasion.

C-ion RT resulted in excellent local control. C-ion RT could become a curative treatment option for HN adenocarcinoma with acceptable toxicities.