1. Department of Surgery Yamaga City Medical Center Kumamoto Japan
2. Department of Hepato‐Biliary‐Pancreatic and Breast Surgery Ehime University Graduate School of Medicine Toon Japan
3. Institute of Gastroenterology, Department of Surgery Tokyo Women's Medical University Shinjuku‐ku Japan
4. Department of Hepatobiliary and Pancreatic Surgery National Cancer Center Hospital East Kashiwa‐shi Japan
5. Department of Gastroenterological Surgery Yokohama City University Graduate School of Medicine Yokohama Japan
6. Hepato‐Biliary‐Pancreatic Surgery Division, Department of Surgery Graduate School of Medicine, The University of Tokyo Bunkyo‐ku Japan
7. Department of Surgery Sano City Hospital Sano Japan
8. Department of Surgery Teikyo University School of Medicine Itabashi‐ku Japan
9. Department of Surgery Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Tokyo Japan
10. Department of Pediatrics Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo‐ku Japan
11. Department of Surgery Teikyo University Hospital Kawasaki Japan
12. Department of Gastrointestinal Chemotherapy Cancer Institute Hospital of Japanese Foundation for Cancer Research Tokyo Japan
13. Department of Biomedical Statistics and Bioinformatics Graduate School of Medicine, Kyoto University Kyoto Japan
14. Sakurajuji Hospital Kumamoto Japan
15. International University of Health and Welfare, Narita Hospital Chiba Japan
16. Tokyo Medical and Dental University Bunkyo‐ku Japan
17. Department of Surgery Utsunomiya Memorial Hospital Utsunomiya Japan
18. Department of Surgery Tokyo Metropolitan Health and Hospitals Corporation Ohkubo Hospital Shinjuku‐ku Japan