Monitoring circulating tumor cells (CTC) in non-measurable metastatic breast cancer (MBC)

Abstract

503 Background: We have previously reported that the presence of 5 or more circulating tumor cells (CTCs) in 7.5 mL of blood from women with measurable disease in metastatic breast cancer (MBC) is associated with a poor outcome (NEJM, 351:8, 781–791, 2004). Here we report the results of the CTC assay in 46 MBC patients with non measurable disease. Methods: CTCs were enumerated in 7.5mL whole blood at baseline and at 3 or 4 week follow-up intervals for a period of six months in 46 patients with non measurable MBC about to start a new systemic therapy. CTCs were immunomagnetically separated and fluorescently labeled using the CellSearch Kit. Only nucleated (DAPI+) cells with the phenotype EpCAM+, Cytokeratin 8, 18 and/or 19+, and CD45- were counted using the CellSpotter Analyzer. Results: Median Progression Free Survival (PFS) and Overall Survival (OS) were determined for patients with <5 or ≥5 CTC /7.5mL at baseline and at first follow-up. The percentage of patients that were alive at 12 months (AL12) after the blood draw, the frequency of patients with 5 or more CTCs and the significance between the two groups of patients (logrank) is indicated in the table below. Conclusions: Data relating the presence of CTCs in non-measurable MBC with PFS and OS were similar to the data previously reported for measurable MBC. The presence of CTC in MBC patients can be used as a surrogate marker for PFS and OS in MBC patients with non-measurable as well as measurable disease. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Immunicon Immunicon