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

Purpose: 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.

Methods And Materials: 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.

Results: 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.

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