1. a Department of Palliative Care and Rehabilitation Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
2. d Department of Family Medicine, Myong Ji Hospital, Kwandong University, College of Medicine, Gyeonggi, Republic of Korea;
3. e Department of Internal Medicine, Kangdong Sacred Heart Hospital, Hallym University, Chuncheon, South Korea;
4. b Clinical Analytics & Informatics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
5. f Department of Internal Medicine, Institute of Health Science, College of Medicine, Gyeongsang National University, Jinju, Republic of Korea
6. c Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA;