1. a Division of Gastrointestinal Oncology, Shizuoka Cancer Center, Shizuoka, Japan;
2. b Yokohama City University Medical Center, Biostatistics and Epidemiology, Yokohama, Japan;
3. c National Cancer Center Hospital, Gastrointestinal Oncology Division, Tokyo, Japan;
4. d National Cancer Center Hospital East, Division of Hepatobiliary and Pancreatic Oncology, Chiba, Japan;
5. e Kinki Unversity Hospital, Department of Medical Oncology, Osaka, Japan;
6. f Shikoku Cancer Center, Department of Internal Medicine, Ehime, Japan;
7. g Aichi Cancer Center Hospital, Department of Endoscopy, Aichi, Japan;
8. h Tohoku University Hospital, Department of Clinical Oncology, Miyagi, Japan;
9. i Cancer Institute Hospital, Department of Medical Oncology, Tokyo, Japan;
10. j Kumamoto Regional Medical Center, Division of Gastroenterology, Kumamoto, Japan;
11. k St. Marianna University School of Medicine, Department of Clinical Oncology, Kanagawa, Japan