Multicenter, phase ii study of gemcitabine and S-1 combination chemotherapy in patients with advanced biliary tract cancer

Takashi Sasaki, Hiroyuki Isayama^*, Yousuke Nakai, Yukiko Ito, Hirofumi Kogure, Osamu Togawa, Nobuo Toda, Ichiro Yasuda, Osamu Hasebe, Iruru Maetani, Naoki Sasahira, Kenji Hirano, Takeshi Tsujino, Minoru Tada, Masao Omata