This is an open-label, randomized, two-arm, parallel group phase II study. Eligible patients will be randomized to each of the two treatment regimens, one of which is gemcitabine and vinorelbine combination therapy (Group A) and the other is gemcitabine monotherapy followed by vinorelbine monotherapy (Group B). Patients In group A monotherapy will receive gemcitabine and vinorelbine in combination, while patients in group B will receive gemcitabine monotherapy until the evidence of disease progression followed by vinorelbine. A total of 82 patients will be enrolled in this study. Patients will be randomized after stratified according to the number of prior chemotherapy including adjuvant chemotherapy and visceral disease. No maximum number of cycles is pre-determined. Patients may continue on study therapy until documented treatment failure.

Patients in group A who discontinue study therapy will proceed to the post-therapy follow-up phase of the study. Patients in group B who discontinue study therapy while treated with gemcitabine will proceed to receive vinorelbine on disease progression. Patients on vinorelbine who discontinue study therapy will proceed to the post-therapy follow-up phase of the study. Further treatment upon discontinuation of study therapy is at the discretion of the investigator. A two arm, open label phase II study without control is appropriate for exploring the efficacy of gemcitabine with concurrent or sequential vinorelbine in this patient population and for evaluating and characterizing toxicities of two treatment approaches, qualitatively and quantitatively. The purpose of randomization in this phase II study is to diminish the possible impact of selection bias on treatment outcome and thus on interpretation of efficacy and safety data.