[1] Yokohama City Univ, Med Ctr, Gastroenterol Ctr, Dept Radiat Oncol, Yokohama, Kanagawa, Japan
[2] Yokohama City Univ, Med Ctr, Gastroenterol Ctr, Dept Surg, Yokohama, Kanagawa, Japan
[3] Yokohama City Univ, Dept Biostat, Yokohama, Kanagawa, Japan
[4] Yokohama City Univ, Grad Sch Med, Dept Oncol, Div Radiat Oncol, Yokohama, Kanagawa, Japan