1. Department of Gastroenterological Surgery Graduate School of Medicine Osaka University Suita Osaka Japan
2. Department of Surgery Hyogo College of Medicine Nishinomiya Hyogo Japan
3. Department of Health Policy and Management School of Medicine Keio University Shinjuku‐kuTokyo Japan
4. The Japanese Society of Gastroenterological Surgery Minato-ku Tokyo Japan
5. Osaka International Cancer Institute Osaka Osaka Japan
6. Department of Biostatistics School of Medicine Yokohama City UniversityYokohama Kanagawa Japan
7. Database Committee The Japanese Society of Gastroenterological SurgeryMinato‐kuTokyo Japan
8. Department of Surgery and Science Graduate School of Medical Sciences Kyushu University Higashi‐kuFukuoka Japan