The aim of this study was to assess the feasibility and safety of hypofractionated carbon-ion radiotherapy (C-ion RT) in patients with stage III non-small cell lung cancer (NSCLC).

Patients with untreated, histologically proven, unresectable stage III NSCLC and not candidates for chemotherapy were included in this study. C-ion RT was planned and administered with 4 Gy (relative biological effectiveness (RBE)) in daily fractions for a total dose of 64 Gy (RBE) without combined chemotherapy. Dose-limiting toxicity (DLT) was defined as suspension of C-ion RT treatment for 2 weeks due to ≥ grade 2 pneumonitis, or any other ≥ grade 3 adverse event, or as any ≥ grade 4 adverse event within 3 months from the start of treatment.

Six patients were treated between June 2013 and December 2014. The planned full dose of C-ion RT (64 Gy (RBE)) was completed in all patients. No patient developed DLT, and no patient experienced toxicities of ≥grade 3 severity. The overall response rate was 100%, and local tumor control was achieved in all patients during the survival period.

Hypofractionated C-ion RT of patients with stage III NSCLC was feasible and well tolerated. Although the number of patients in this study was small, the results support further investigations to confirm the long-term therapeutic efficacy of this treatment.