1. Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
2. Department of Surgery, Hyogo College of Medicine, Nishinomiya, Japan
3. Department of Surgery, Cancer Institute Hospital, Tokyo, Japan
4. Department of Surgery, Kanagawa Cancer Centre, Yokohama, Japan
5. Department of Surgery, Tokyo Metropolitan Cancer and Infectious Disease Centre, Komagome Hospital, Tokyo, Japan
6. Department of Surgery, Niigata Cancer Centre Hospital, Niigata, Japan
7. Department of Gastroenterological Surgery, Aichi Cancer Centre Hospital, Nagoya, Japan
8. Department of Surgery, National Hospital Organization Shikoku Cancer Centre, Matsuyama, Japan
9. Japan Clinical Oncology Group Data Centre, National Cancer Centre, Tokyo, Japan