Although around a long time in Japan, S-1 or TS-1 seems to be available only in study. Maybe in CT:
http://her2support.org/vbulletin/sho...&highlight=S-1
Maybe there are other antimetabolites to consider: Ixempra, Methotrexate
Even so..if Gemzar, not the cancer is elevating the LFT, that might suggest continuing it showing other signs of working.