1. Department of Gastroenterological and Pediatric Surgery, Oita University Faculty of Medicine, Yufu, Japan
2. Biostatistics Center, Kurume University, Kurume, Japan
3. Department of Upper Gastrointestinal Surgery, Saitama Medical University International Medical Center, Hidaka, Japan
4. Department of Gastroenterological Surgery, Ishikawa Prefectural Central Hospital, Kanazawa, Japan
5. Department of General and Gastroenterological Surgery, Osaka Medical and Pharmaceutical University, Takatsuki, Japan
6. Department of Gastroenterology and Pediatric Surgery, Gifu University, Gifu, Japan
7. Department of Medical Safety Science, Iwate Medical University School of Medicine, Shiwa, Japan
8. Department of Upper Gastrointestinal Surgery, Kitasato University School of Medicine, Sagamihara, Japan
9. Department of Surgery, Gastroenterological Center, Yokohama City University, Yokohama, Japan
10. Department of Gastrointestinal Surgery, Tokyo Medical and Dental University, Yushima, Japan
11. Department of Gastrointestinal Surgery, Hyogo Cancer Center, Akashi, Japan
12. Department of Surgery, Hakodate Goryoukaku Hospital, Hakodate, Japan
13. Department of Gastroenterological Surgery, Aichi Cancer Center Hospital, Nagoya, Japan
14. Department of Gastric Surgery, National Cancer Center Hospital East, Kashiwa, Japan
15. Department of Surgery, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Honkomagome, Japan
16. Department of Gastroenterological Surgery, Osaka University, Suita, Japan
17. Department of Gastric Surgery, Cancer Institute Hospital, Ariake, Japan
18. Department of Comprehensive Surgery for Community Medicine, Oita University Faculty of Medicine, Yufu, Japan
19. Oita University, Yufu, Japan
20. for the Japanese Laparoscopic Surgery Study Group (JLSSG)