Detection and significance of circulating tumor cells (CTC) in patients with metastatic pancreatic cancer (PC) receiving systemic therapy

Abstract

4596 Background: Detection of CTC in the peripheral circulation of pts with solid tumors may provide useful prognostic and predictive information. In a previously reported pilot study, we detected CTC in approx 2/3rds of pts with all stages of PC using a flow cytometric-based approach. This study examines the significance of CTC using two separate methods in pts with metastatic PC undergoing systemic rx. Methods: Blood was obtained at baseline and after 2 months of rx from pts with metastatic PC participating in a phase II trial of gemcitabine, cisplatin, and bevacizumab. Two methods for measuring CTC were tested: immunomagnetic capture/flow cytometry (IC/FC) using anti-EpCAM Abs, and the Veridex CellSearch system. Wilcoxon Rank tests were used to test the association of CTC concentration at each time point, and change in concentration over time, with overall survival, time to tumor progression, and CA19–9 response. Results: CTC were measured in 48 indiv pts at baseline (31 using IC/FC, 23 using CellSearch, 6 using both methods) and in 39 indiv pts after 2 months of rx (20 IC/FC, 23 CellSearch, 4 both methods). No correlation was found between CTC concentration at either baseline or at 2 mos and any clinical endpoints (see table ). This was true for both IC/FC and CellSearch methods. 25 pts had serial CTC measurements using consistent methods at both time points (17 IC/FC, 12 CellSearch, 4 both methods). CTC concentration decreased in 9 of 17 pts (52.9%) tested by IC/FC and in 5 of 12 pts (41.7%) tested by CellSearch; however, change in CTC concentration over time was not associated with clinical outcomes. Too few pts have been tested by both methods at a given time point to establish a significant correlation betw the two methods. Conclusions: CTC can be detected in pts with metastatic PC using both methods tested in this study, albeit at low concentrations. The small sample size to date precludes our ability to determine the prognostic and predictive significance of these cells in this disease setting. [Table: see text] No significant financial relationships to disclose.