Abstract 2687: Development of a new, highly sensitive assay for circulating tumor cell (CTC) detection based on the CellSearch® CTC Profile Kit enrichment and laser scanning cytometry analysis

Abstract

Abstract The presence of CTCs in the peripheral blood, as detected by the FDA-approved CellSearch® CTC Kit, is associated with decreased overall and progression free survival in patients with metastatic breast, prostate and colorectal cancers. In addition to CTC enumeration, CellSearch® CTC Kit provides a unique tool for CTC biomarker analysis in cancers of epithelial origin (CD45—, EpCAM+, and cytokeratins (CK) 8,18-positive and/or 19-positive). Considerable cell loss is suspected to occur at many of the automated steps of the CellSearch® CTC process, resulting in undermined recovery of CTCs. Herein, we demonstrate an improved, highly sensitive approach for CTC enumeration, which is based on the CellSearch® CTC Profile Kit and immunofluorescent analysis using LSC. The initial blood processing was conducted using the CellSearch® CTC Profile Kit from Veridex and the CellTracks® AutoPrep® system, which allowed recovery of the EpCAM+ cells directly from the instrument. Next, EpCAM+ cell population was subjected to manual immunofluorescent labeling with antibodies against CK and CD45, and CTCs were enumerated by LSC, based on the standard CellSearch® CTC criteria. When we compared this new method to standard CTC enumeration in patients with various cancer types including head and neck, renal cell, basal cell, prostate, non-small cell lung, sebaceous gland and ovarian cancers, we consistently detected higher CTC counts in samples analyzed with the new method. Indeed, 88% of patients (79 out of 90) were CTC-negative based on the standard analysis, while only 37% of patients were CTC-negative based on the CTC Profile Kit/LSC data. We next conducted a side-by-side comparison of the two techniques in patients with hepatocellular carcinoma (HCC, EpCAM-low) and prostate cancer (EpCAM+). CTC Profile Kit/LSC method demonstrated up to a 470% increased CTC recovery in the prostate cancer samples. Remarkably, it also allowed isolation of CTCs from the CTC-negative (as detected by the standard kit) HCC and prostate cancer samples. Finally, the new CTC enumeration method consistently yielded higher CTC counts in patients enrolled in a Phase I clinical trial of Bevacizumab and Cediranib. Importantly, our preliminary analysis indicated that changes in CTC counts from baseline to 24 h post-therapy, as measured by the new method, may correlate with changes in tumor size. In conclusion, we developed a new CellSearch® CTC Profile Kit/LSC-based method that offers higher sensitivity of CTC recovery and thus provides a broader capability for downstream molecular characterization. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2687.