Evaluation of Tumor Factors in Breast Cancer Treated With Docetaxel and Capecitabine

Some chemotherapy drugs are thought to work in synergy, meaning they work better in combination, rather than singly because one drug may cause changes in the tumor that will make the other drug more effective. The drugs docetaxel and capecitabine may work in synergy, based on laboratory studies in tumors. These laboratory studies show that docetaxel increases the levels of a critical enzyme, called thymidine phosphorylase (TP), which is necessary to activate the capecitabine. This study will use this promising chemotherapy combination in patients with breast cancer. Before, during, and after chemotherapy, the participants' breast tumors will be examined to see if TP increases, as predicted by the laboratory studies. The study will also look at other factors in tumors and blood that may be able to predict how effective the chemotherapy will be for each individual, so that in the future we may better select the best chemotherapy for an individual's cancer.