Association of Dihydropyrimidine Dehydrogenase (DPYD) Variants With Toxicity Related to Capecitabine

The goal of this laboratory research study is to identify possible differences in a gene among patients with breast cancer that cannot be treated by surgery. Researchers want to find out if differences in this gene may increase the risk of side effects from capecitabine.

If you agree to take part in this study, 1 blood sample (about 2 tablespoons) will be drawn for use in genetic research. If you are unable to provide a blood sample, researchers will collect leftover tissue samples from your previously collected tumor tissue (from the time of the breast cancer diagnosis). The tumor samples will be used for genetic research. After the blood draw or tissue collection, your participation in this study will be over. The blood samples for the genetic research will be stored at Myriad Laboratories. Before your blood and/or tissue is sent to Myriad Laboratories for banking, your name and any personal identifying information will be coded to protect your privacy. M. D. Anderson will not have oversight of any leftover tissue and/or blood that will be banked by Myriad Laboratories for additional research. This is an investigational study. Up to 210 patients will take part in this study. All will be enrolled at M. D. Anderson.