1. Department of Family Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Family Medicine, Hallym University Chuncheon Sacred Heart Hospital, Hallym University College of Medicine, Chuncheon, Korea.
3. Department of Family Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
4. Carcinogenesis Research Branch, Research Institute, National Cancer Center, Goyang, Korea.
5. Family Medicine Clinic, National Cancer Center Hospital, National Cancer Center, Goyang, Korea.