1. Department of Anesthesiology and Pain Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
2. Division of Biostatistics, Department of R&D Management, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
3. Division of Biostatistics, Biostatics Collaboration Team, Research Core Center, National Cancer Center, Gyeonggi-do, Republic of Korea.