1. Department of Surgery, Tohoku University School of Medicine, Sendai, Japan
2. Hepatobiliary and Pancreatic Surgery Division, National Cancer Center Hospital, Tokyo, Japan
3. Hepatobiliary and Pancreatic Oncology Division, National Cancer Center Hospital, Tokyo, Japan
4. Second Department of Surgery, Wakayama Medical University, Wakayama, Japan
5. Department of Surgery, Kansai Medical University, Osaka, Japan
6. Department of Surgery, Nara Medical University, Nara, Japan
7. Department of Surgery, Tokyo Metropolitan Cancer and Infectious Diseases Center, Komagome Hospital, Tokyo, Japan
8. Department of Surgery, Kindai University Faculty of Medicine, Osaka, Japan
9. Department of Surgery, Teikyo University School of Medicine, Tokyo, Japan
10. Department of Medical Oncology, Kyorin University Faculty of Medicine, Tokyo, Japan
11. Department of Biostatistics, School of Public Health, University of Tokyo, Tokyo, Japan