1. Hyogo Ion Beam Medical Center Department of Radiology, , 1-2-1 Kouto, Shingu-cho, Tatsuno, Hyogo 679-5165, Japan
2. National Institutes for Quantum and Radiological Science and Technology, QST Hospital , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
3. Hyogo Ion Beam Medical Center Kobe Proton Center Department of Radiation Oncology, , 1-6-8 Minatojima Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
4. Kyoto Prefectural University of Medicine Department of Radiology, , Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan
5. Kanagawa Cancer Center Department of Radiation Oncology, , 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa 241-8515, Japan
6. Proton Therapy Center, Fukui Prefectural Hospital , 2-8-1, Yotsui, Fukui, Fukui 910-8526, Japan
7. Department of Radiation Oncology, Southern TOHOKU Proton Therapy Center , 7-172, Yatsuyamada, Fukushima, Koriyama 963-8052, Japan
8. Hokkaido University Hospital Department of Radiation Oncology, , Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-0808, Japan
9. Hokkaido University Department of Radiation Oncology, Faculty of Medicine, , Kita14, Nishi5, Kita-Ku, Sapporo, Hokkaido 060-8648, Japan
10. University of Tsukuba Radiation Oncology & Proton Medical Research Center, Faculty of Medicine, , 2-1-1, Amakubo, Tsukuba, Ibaraki 305-8576, Japan
11. National Cancer Hospital East Department of Radiation Oncology, , 6-5-1, Kashiwanoha, Kashiwa, Chiba 277-8577, Japan
12. Graduate School of Medicine, Tohoku University Department of Surgery, , 1-1, Seiryomachi, Aoba-ku, Sendai, Miyagi 980-8574, Japan
13. Graduate School of Medicine, Kyoto University Department of Therapeutic Oncology, , 53 Shougoin Kawaharachou, Sakyo-ku, Kyoto 606-8507, Japan
14. Hyogo College of Medicine Department of Biostatistics, , 1-1, Mukogawacho, Nishinomiya, Hyogo 663-8501, Japan