Capecitabine comes as a tablet to take by mouth. It is usually taken twice a day (in the morning and in the evening) for 2 weeks, followed by a 1 week break before repeating the next dosage cycle. In this study, capecitabine will be prescribed as dosage of 900mg/m2, and maintain for a whole year after the standard treatment in operable triple negative breast cancer patients. DFS is set as the primary outcome, OS and DDFS are also observed as the secondary outcomes. Statistical analysis are made to see whether this metronomic therapy of capecitabine ( 900mg/m2) will bring benefit to any of the iterms above.