Salvage Treatment Using Carbon Ion Radiation in Patients With Locoregionally Recurrent Nasopharyngeal Carcinoma: Initial Results

BACKGROUND: Reirradiation for locoregionally recurrent nasopharyngeal carcinoma (NPC) after a definitive dose of radiotherapy (RT) is challenging and usually associated with severe toxicities. Intensity-modulated carbon ion RT (IMCT) offers physical/biologic advantages over photon-based intensity-modulated RT. Herein, the authors report their initial experience of IMCT in previously irradiated patients with locoregionally recurrent NPC. METHODS: Patients with locoregionally recurrent, poorly differentiated or undifferentiated NPC who underwent salvage therapy with IMCT at the Shanghai Proton and Heavy Ion Center between May 2015 and August 2017 were included in the current study. The IMCT doses were 50 to 66 Gray equivalent (GyE) (2.0-3.0 GyE/daily fraction), delivered via raster scanning technology. The 1-year overall survival, disease-specific survival, progression-free survival (PFS), local recurrence-free survival, regional recurrence-free survival, and distant metastasis-free survival were calculated. Univariate and multivariate analyses of PFS were performed to identify possible predictive factors. RESULTS: Among the 75 patients included, 4 patients, 14 patients, 29 patients, and 28 patients, respectively, had recurrent American Joint Committee on Cancer stage I, stage II, stage III, and stage IVA/B disease. With a median follow-up of 15.4 months (range, 2.6-29.7 months), the 1-year overall survival, disease-specific survival, PFS, local recurrence-free survival, regional recurrence-free survival, and distant metastasis-free survival rates were 98.1%, 98.1%, 82.2%, 86.6%, 97.9%, and 96.2%, respectively. A higher fraction size of 3 GyE (vs <3 GyE) or a higher biological equivalent dose significantly improved the PFS rate on univariate analysis, but not on multivariate analysis. No patient developed acute toxicity of grade 2 during IMCT. Late treatment-induced severe (grade 3 or 4) toxicities were infrequent, but included mucosal necrosis (9.3%), xerostomia (1.3%), and temporal lobe necrosis (1.3%). CONCLUSIONS: This initial experience in the first 75 patients with locoregionally recurrent NPC was encouraging. Carbon ion RT could provide promising survival rates with infrequent severe toxicities for patients with locoregionally recurrent NPC. (C) 2018 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution- NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.