JCOG Data Center/Operations Office, National Cancer Center Hospital, Tokyo, Japan. Division of Gastrointestinal Oncology, Shizuoka Cancer Center, Shizuoka, Japan. Electronic address: a.fukutomi@scchr.jp. Clinical Research Center, National Hospital Organization Shikoku Cancer Center, Shizuoka, Japan. Department of Hepatobiliary and Pancreatic Oncology, Osaka International Cancer Institute, Japan. Department of Hepatobiliary and Pancreatic Oncology, National Cancer Center Hospital, Japan. Department of Gastroenterology, Hepatobiliary and Pancreatic Medical Oncology Division, Kanagawa Cancer Center, Japan. Department of Hepatobiliary and Pancreatic Oncology, National Cancer Center Hospital East, Japan. Department of Gastroenterology, Aichi Cancer Center Hospital, Japan. Department of Gastroenterology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Japan. Department of Medical Oncology, Kyorin University Faculty of Medicine, Tokyo, Japan.