1. a Department of Palliative Care and Rehabilitation Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
2. b Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA;
3. c Department of Internal Medicine, Institute of Health Science, College of Medicine, Gyeongsang National University, Jinju, Korea;
4. d Department of Family Medicine, Myong Ji Hospital, Kwandong University College of Medicine, Gyeonggi, Korea