Prospective study of a rotating gantry with scanning beams of carbon-ion radiotherapy for choroidal malignant melanoma.

To evaluate the safety of a rotating gantry with scanning beams of carbon-ion radiotherapy (C-ion RT) for choroidal malignant melanoma. A prospective study of C-ion RT using a rotating gantry with scanning beams for choroidal malignant melanoma was initiated at the National Institute for Quantum Science and Technology, QST Hospital in March 2018. The inclusion criteria were as follows: (i) clinically diagnosed ocular/choroidal malignant melanoma; (ii) tumor measurable by imaging tests; (iii) score of 0-2 on the Eastern Cooperative Oncology Group Performance Status scale and (iv) ability to provide consent for treatment. All patients received 68 Gy in four fractions of C-ion RT by a rotating gantry with scanning beams. Between April 2018 and July 2019, 21 patients were enrolled and underwent C-ion RT as planned. All 21 patients completed the treatment schedule and the 3-year follow-up period. The median duration of follow-up was 43 months (range, 35.2-54.6 months). Regarding late normal tissue responses, three of the 21 patients developed grade 2 neovascular glaucoma; however, no other late grade ≥2 acute toxicities were observed. During the 3-year study period, all 21 patients survived with no local recurrence; none of the patients underwent enucleation. Three cases showed liver metastasis. The 3-year local control, overall survival and eye-retention rates were all 100%. The results of this prospective study confirmed that the effectiveness and safety of this method are equivalent to those of conventional passive irradiation methods, although the number of cases was small. The results of this prospective study confirmed that the effectiveness and safety of this method are equivalent to those of conventional passive irradiation methods, although the number of cases was small.