Prognostic impact of changes in circulating tumor cells (CTC) in metastatic breast cancer (MBC).

11012 Background: To prospectively assess the prognostic value of CTC counts at baseline and after one cycle of therapy and their kinetics for response, progression-free (PFS), and overall survival (OS) in MBC. Methods: MBC patients underwent CTC enumeration (CellSearch, Veridex) at baseline (CTCBL), after one cycle of a new line of therapy (CTC1C), and at progression (CTCPD). CTC status was classified as negative (neg (−)) or positive (pos (+)) for neg) or became neg (pos>neg), or as unfavorable (neg>pos or pos>pos). Tumor response was assessed every 2–3 months using RECIST criteria. CTC status and kinetics were associated with outcome using log-rank and Fisher’s exact tests. Results: Of 326 patients enrolled (median age (range) at first diagnosis: 50 (23–81) years), 115/326 (35%) were CTCBL+, 51/162 (31%) were CTC1C+, and 39/108 (36%) were CTCPD+. Median f...