1. Hokkaido University Hospital Department of Radiation Oncology, , Sapporo, Hokkaido 060-8638, Japan
2. University of Tsukuba Department of Radiation Oncology, , Tsukuba, Ibaraki 305-8575, Japan
3. Nippon Medical School Hospital Division of Radiation Oncology, , Tokyo 113-8602, Japan
4. Hokkaido University Global center for Biomedical Science and Engineering, Faculty of Medicine, , Sapporo, Hokkaido 060-8638, Japan
5. Kyoto University Graduate School of Medicine Department of Neurosurgery, , Kyoto 606-8507, Japan
6. Hamamatsu University School of Medicine Department of Neurosurgery, , Hamamatsu, Shizuoka 431-3192, Japan
7. Fukui Prefectural Hospital Proton Therapy Center, , Fukui, Fukui 910-8526, Japan
8. Tsuyama Chuo Hospital Department of Radiology, , Tsuyama, Okayama 708-0841, Japan
9. Sapporo Teishinkai Hospital Proton Therapy Center, , Sapporo, Hokkaido 065-0033, Japan
10. Hyogo Ion Beam Medical Center Department of Radiology, , Tatsuno, Hyogo 679-5165, Japan
11. Southern Tohoku Proton Therapy Center Department of Radiation Oncology, , Koriyama, Fukushima 963-8563, Japan
12. Promotion Unit, Institute of Health Science Innovation for Medical Care, Hokkaido University Hospital Data Science Center, , Sapporo, Hokkaido 060-8638, Japan
13. National Cancer Center Hospital East Department of Radiation Oncology, , Kashiwa, Chiba 277-8577, Japan
14. Faculty of Medicine and Graduate School of Medicine, Hokkaido University Department of Radiation Oncology, , Sapporo, Hokkaido 060-8638, Japan