781 Background: Breast cancer is one of the most common malignancies among Chinese women and the rate of new cases has risen during the past 20 years. 5-FU + N is an effective palliative regimen for MBC. N upregulates thymidine phosphorylase, a key enzyme in the conversion of X to active 5-FU within tumors. In several studies, the combination of X + N led to response rates ranging from 43–67% in first-line MBC. Therefore, we evaluated the efficacy and safety of X + N in Chinese pts with MBC refractory to anthracycline or taxane treatment. Methods: 77 pts were enrolled between Feb 2003 and Nov 2004. All pts had measurable MBC (WHO) recurrent after anthracycline or taxane treatment, Karnofsky PS ≥60, adequate bone marrow, renal and hepatic function. Pts received 3-weekly cycles of oral X 1000mg/m2 bid on days 1–14 + i.v. N 25mg/m2 on days 1 and 8, for at least 2 cycles. Pts with PD went off study while those with CR, PR, or SD continued treatment for a maximum of 6 cycles. Results: Baseline characteristics of the 77 pts evaluable to date: median age 51 years (range 29–68); median Karnofsky PS 90 (range 70–100). Previous chemotherapy was: anthracycline (87%), paclitaxel/docetaxel (52%). Principal tumor sites were: lung (40%), liver (39%), lymph nodes (33%), thoracic wall (12%), breast (7%), other (3%). All pts received at least 2 cycles, 20 received 4 cycles and 47 received 6 cycles. Efficacy findings are shown in the table. Median progression-free and overall survival have not yet been reached. The most common (≥10% pts) treatment-related grade 1/2 adverse events were: HFS (16%), nausea (12%), and SGPT abnormality (10%). Most adverse events improved or resolved after dose adjustment and/or suitable treatments. There were very few grade 3/4 adverse events, the most common being leucopenia (12%). Conclusions: X + N is highly active in MBC and its efficacy is confirmed in this study in Chinese pts. The combination is also well tolerated. No significant financial relationships to disclose.