1. Department of Family Medicine; Korea University Guro Hospital; Seoul South Korea
2. Department of Family Medicine; Catholic University St. Paul's Hospital; Seoul South Korea
3. Department of Family Medicine; Gachon University Gil Medical Center; Incheon South Korea
4. Department of Palliative Medicine; Catholic University Seoul St. Mary's Hospital; Seoul South Korea
5. Department of Family Medicine; Ilsan Hospital; Goyang South Korea
6. Department of Family Medicine; Kyungpook National University Medical Center; Daegu South Korea
7. Department of Statistics; Dongguk University; Seoul South Korea
8. Division of Hematology and Oncology, Department of Internal Medicine; Ulsan University Hospital; Ulsan South Korea