First prospective feasibility study of carbon-ion radiotherapy using compact superconducting rotating gantry

Objective: We had developed compact rotating gantry for carbon ion using superconducting magnets in 2015 which became clinically operational in 2017. The objective of this study was to assess the clinical feasibility and safety of using compact rotating gantry with three-dimensional active scanning in delivery of carbon-ion radiotherapy (C-ion RT) for relatively stationary tumours. Methods: A prospective feasibility study was conducted with 10 patients who had been treated with C-ion RT using compact rotating gantry between April 2017 and April 2018 at Hospital of the National Institute of Radiological Sciences (NIRS) for head and neck and prostate cancers. The primary end point was evaluation of acute toxicities within 3 months of starting C-ion RT. Results: Out of 10 cases 8 were of head and neck cancers and 2 were of prostate cancers. All of those eight head and neck cases were of locally advanced stages. Both of the prostate cancer patients belong to intermediate risk categories. None of the patients developed even Grade 2 or more severe skin reactions. Six out of eight cases with head and neck cancers experienced Grade 2 mucosal reactions; however, nobody developed Grade 3 or more severe mucosal reactions. There was no gastrointestinal reaction observed in prostate cancer patients. One patient developed Grade 2 genitourinary reaction. Conclusion: C-ion RT using compact rotating gantry and three-dimensional active scanning is a safe and feasible treatment for relatively less mobile tumours. Advances in knowledge: This study will be the first step to establish the use of superconducting rotating gantry in C-ionRT in clinical setting paving the way for treating large number of patients and make it a standard of practice in the future.