[1] Hokkaido Univ Hosp, Dept Gastroenterol & Hepatol, Sapporo, Hokkaido, Japan
[2] Hokkaido Univ Hosp, Div Canc Ctr, Sapporo, Hokkaido, Japan
[3] Obihiro Kosei Gen Hosp, Dept Gastrointestinal Surg, Obihiro, Hokkaido, Japan
[4] Hakodate Municipal Hosp, Dept Gastroenterol, Hakodate, Hokkaido, Japan
[5] Kushiro Rosai Hosp, Dept Med Oncol, Kushiro, Japan
[6] Teine Keijinkai Hosp, Dept Med Oncol, Sapporo, Hokkaido, Japan
[7] Hokkaido Med Ctr, Natl Hosp Org, Dept Gastroenterol, Sapporo, Hokkaido, Japan
[8] Nakadori Gen Hosp, Dept Gastrointestinal Surg, Akita, Japan
[9] Muroran City Gen Hosp, Dept Gastroenterol, Muroran, Hokkaido, Japan
[10] Sapporo Med Univ, Sch Med, Dept Med Oncol, Sapporo, Hokkaido, Japan
[11] Japanese Red Cross Kitami Hosp, Dept Gastroenterol, Kitami, Hokkaido, Japan