Treatment outcomes of particle radiotherapy using protons or carbon ions as a single-modality therapy for adenoid cystic carcinoma of the head and neck

Abstract

Background and purpose: The aim of this study was to retrospectively analyse the outcomes of cases of adenoid cystic carcinomas (ACCs) of the head and neck that were treated at a single institution with particle therapy consisting of either protons or carbon ions.

Methods and materials: Between February 2002 and March 2012, 80 patients were treated with proton therapy (PT) or carbon ion therapy (CIT) alone. PT and CIT were employed in 40 (50%) patients each, and more than half of the patients received 65.0 GyE in 26 fractions (n=47, 59%).

Results: The median duration of follow-up was 38 months (range, 6-115 months). For all patients, the 5-year for overall survival (OS) rate, progression-free survival (PFS) rate, and local control (LC) rate were 63%, 39%, and 75%, respectively. No significant differences between PT and CIT were observed. The 5-year LC rates for T4 and inoperable cases were 66% and 68%, respectively. Twenty-one patients (26%) experienced grade 3 or greater late toxicities, including three patients who developed grade 5 bleeding from nasopharyngeal ulcers.

Conclusions: Particle radiotherapy for ACC achieves favourable LC, and its efficacy in inoperable or T4 cases is promising. There were no significant differences between PT and CIT in terms of OS, PFS and LC.

Keywords: Adenoid cystic carcinoma; Carbon ion therapy; Particle therapy; Proton therapy.