1. Department of Gastroenterological Surgery, Graduate School of Medicine; Yokohama City University; Yokohama Japan
2. Department of Surgery; Teikyo University Chiba Medical Center; Chiba Japan
3. Department of Surgery, Gastroenterological Center; Yokohama City University; Yokohama Japan
4. Department of Surgery; Yokosuka Kyosai Hospital; Yokosuka Japan
5. Department of Surgery; Yokohama City Hospital; Yokohama Japan
6. Department of Surgery; Yokohama Ekisaikai Hospital; Yokohama Japan
7. Department of Surgery; Saiseikai Yokohamashi Nanbu Hospital; Yokohama Japan
8. Department of Surgery; Ito Municipal Hospital; Ito Japan
9. Department of Surgery; Saiseikai Wakakusa Hospital; Yokohama Japan
10. Department of Biostatistics; Center for Novel and Exploratory Clinical Trials; Yokohama City University; Yokohama Japan