[1] Teikyo Univ, Chiba Med Ctr, Dept Surg, Ichihara, Chiba 2990111, Japan
[2] Yokohama City Univ, Grad Sch Med, Dept Surg Gastroenterol, Yokohama, Kanagawa 232, Japan
[3] Yokohama City Univ, Grad Sch Med, Dept Clin Oncol, Yokohama, Kanagawa 232, Japan
[4] Yokohama City Univ, Grad Sch Med, Dept Biostat & Epidemiol, Yokohama, Kanagawa 232, Japan
[5] Yokohama City Univ, Med Ctr, Div Diagnost Pathol, Yokohama, Kanagawa 232, Japan