1. Department of Surgery, Dongguk University Ilsan Hospital, Dongguk University College of Medicine, Goyang, Korea.
2. Department of Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Biostatistics, Dongguk University Ilsan Hospital, Dongguk University College of Medicine, Goyang, Korea.
5. Department of Surgery, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea.