1. Department of Surgery, Kyung Hee University Medical Center, Kyung Hee University School of Medicine, Seoul, Korea.
2. Department of Surgery, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea.
3. Department of Surgery, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
4. Department of Surgery, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
5. The Korea Central Cancer Registry, Division of Cancer Registration and Surveillance, National Cancer Center, Goyang, Korea.