1. Department of Radiology, Kyoto Prefectural University of Medicine , Kyoto 602-8566 , Japan
2. Department of Radiation Oncology , Nagoya Proton Therapy Center, , Nagoya 462-8508 , Japan
3. Nagoya City University West Medical Center , Nagoya Proton Therapy Center, , Nagoya 462-8508 , Japan
4. QST Hospital, National Institutes for Quantum Science and Technology , Chiba 263-8555 , Japan
5. Department of Biostatistics, Kyoto Prefectural University of Medicine , Kyoto 602-8566 , Japan
6. Department of Radiation Oncology, Kobe Proton Center , Hyogo 650-0047 , Japan
7. Department of Radiation Oncology, Gunma University Graduate School of Medicine , Gunma 371-8511 , Japan
8. Department of Radiation Oncology, Yamagata University, Faculty of Medicine , Yamagata 990-9585 , Japan
9. Department of Radiology, Southern Tohoku Proton Therapy Center , Koriyama City, Fukushima 963-8052 , Japan
10. Department of Radiation Oncology, University of Tsukuba , Ibaraki 305-8550 , Japan
11. Proton Therapy Center, Fukui Prefectural Hospital , Fukui 910-0846 , Japan
12. Department of Radiation Oncology, National Cancer Center Hospital East , Chiba 277-8577 , Japan
13. Department of Radiology, Hyogo Ion Beam Medical Center , Hyogo , Japan
14. Department of Gastrointestinal Oncology, National Cancer Center Hospital East , Chiba , Japan
15. Department of Gynecology and Obstetrics, Kyoto University Graduate School of Medicine , Kyoto 606-8501 , Japan
16. Department of Radiation Oncology, Hokkaido University Faculty of Medicine , Hokkaido 060-0808 , Japan