1. Department of Family Medicine, Yonsei University College of Medicine, Seoul, Korea
2. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea
3. Department of Family Medicine, Sungkyunkwan University School of Medicine, Seoul, Korea
4. Supportive Care Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea