Affiliations:
  1. Department of Radiation Oncology, Sano Kosei General Hospital, 1728, Horigome-machi, Sano, Tochigi, 327-8511, Japan.
  2. Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan.
  3. Gunma University Heavy Ion Medical Center, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan.
  4. Department of Gastroenterology, Sano Kosei General Hospital, 1728, Horigome-machi, Sano, Tochigi, 327-8511, Japan.