1. Department of Surgery; Toho University School of Medicine; Tokyo Japan
2. Gastric Surgery Division; National Cancer Center Hospital; Tokyo Japan
3. Department of Surgery; National Hospital Organization Kumamoto Medical Center; Kumamoto Japan
4. Department of International Medical Cooperation; Graduate School of Medical Sciences Kumamoto University; Kumamoto Japan
5. Department of Biostatistics; School of Public Health; Graduate School of Medicine; The University of Tokyo; Tokyo Japan
6. Interfaculty Initiative in Information Studies; Graduate School of Interdisciplinary Information Studies; The University of Tokyo; Tokyo Japan