1. Department of Minimally Invasive Surgical and Medical Oncology, Fukushima Medical University, Fukushima City, Fukushima, Japan
2. Department of Radiology, Southern Tohoku Proton Therapy Center, Koriyama City, Fukushima, Japan
3. Department of Surgery, Southern Tohoku General Hospital, Koriyama City, Fukushima, Japan
4. Department of Gastroenterology, Southern Tohoku General Hospital, Koriyama City, Fukushima, Japan