1. Department of Gastrointestinal Oncology, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo, Japan.
2. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
3. Department of Gastroenterology, Kawasaki Municipal Hospital, Kawasaki, Japan.
4. Biostatistics Unit, Clinical and Translational Research Center, Keio University Hospital, Tokyo, Japan.