1. Proton Therapy Center, Fukui Prefectural Hospital, 2-8-1 Yotsui, Fukui City 910-8526, Fukui Prefecture, Japan
2. Department of Gastroenterology, Fukui Prefectural Hospital, 2-8-1 Yotsui, Fukui City 910-8526, Fukui Prefecture, Japan
3. Department of Radiotherapy, Kanazawa University Hospital, Kanazawa 920-8641, Ishikawa, Japan