nab-paclitaxel should be given intravenously on days 1 and 8 at a dose as follows, Treatment should be repeated every 3 weeks: Treatment arm A：125 mg /m2; Treatment arm B：100 mg /m2; Treatment arm C: 80 mg /m2; S-1 should be given orally twice a day as follows for 14 consecutive days, followed by a 1-week rest. Treatment should be repeated every 3 weeks. BSA ＜ 1.5 m2，40mg，bid;BSA ≥ 1.5 m2，50mg，bid.