A high level of circulating tumor cells (CTCs) — cells that have detached from a tumor and are circulating in the body through the blood — are an independent prognostic marker in metastatic breast cancer as first-line therapy. In addition, persistence of high CTC level during therapy was found to be an early marker of poor outcome. “This is the largest, prospective series validating the prognostic value of CTCs in first- line chemotherapy metastatic breast cancer, independently from serum tumor markers for overall survival,” said Jean-Yves Pierga, M.D., Ph.D., professor of the medical oncology department, Institut Curie and Université Paris Descartes, France. “Persistence of a high level of CTCs before the second cycle of chemotherapy was a strong and early predictive marker of poor outcome.” Pierga presented results of this study at the 33rd Annual CTRC-AACR San Antonio Breast Cancer Symposium, held here Dec. 8-12, 2010