1. Division of Pulmonology, Department of Internal Medicine, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
5. Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, Korea.
6. Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.