[1] Seoul Natl Univ, Bundang Hosp, Dept Internal Med, Div Hematol & Med Oncol,Coll Med, Seongnam, South Korea
[2] Chungnam Natl Univ Hosp, Dept Family Med, Daejeon, South Korea
[3] Dongguk Univ, Dept Family Med, Ilsan Hosp, Goyang, South Korea
[4] Dongguk Univ, Dept Med, Med Sch, Seoul, South Korea
[5] Takeda Gen Hosp, Dept Palliat Med, Aizu Wakamatsu, Fukushima, Japan
[6] Tohoku Univ, Dept Palliat Med, Sch Med, Sendai, Miyagi, Japan
[7] CHA Univ, Bundang Med Ctr, Div Med Oncol, Seongnam, South Korea
[8] Yonsei Univ, Yonsei Canc Ctr, Dept Internal Med, Div Med Oncol,Coll Med, Seoul, South Korea
[9] Dongguk Univ, Dept Stat, Med Sch, Seoul, South Korea