Abstract 1601: Clinical performance of the AccuCyte® - CyteFinder® System, a dual-technology platform for comprehensive collection and high resolution imaging of circulating tumor cells

High numbers of circulating tumor cells (CTC) predict poor prognosis. In addition, serial monitoring of CTC numbers may be used to assess response to therapy or progressing disease. The AccuCyte® - CyteFinder® (AC/CF) system combines density-based collection of all nucleated blood cells with high-resolution digital microscopic imaging, image analysis and single-cell retrieval. The AccuCyte® kit contains a novel separation tube, transfer device, and spreader for simple collection of nucleated cells onto microscopic slides compatible with automated immunostaining. CyteFinder® is a high-resolution fluorescent scanner with image analysis, review software and integrated CytePicker™ module for single-cell retrieval. In a blinded study we directly compared the AC/CF platform to the CellSearch® System (Veridex), the only FDA-cleared CTC platform, which relies on magnetic capture of cells that express EpCAM. We first compared recovery of model CTCs (mCTCs) using tumor cell lines with high EpCAM expression (MCF7 and LNCaP) or low EpCAM expression (PC3 and A549) in paired spike-in samples. CTCs were identified by positive cytokeratin and nuclear staining and an absence of CD45 staining. AC/CF and CellSearch® detected similar numbers of mCTCs from high-EpCAM lines (AC/CF average: 91.5% for MCF7 and 92% for LNCaP; CellSearch® average: 87% for MCF7 and 85% for LNCaP). AC/CF detected more cells from low-EpCAM lines, finding an average of 69% more PC3 cells and 57% more A549 cells. These results suggest that CellSearch® captures low-EpCAM cells inefficiently. We next compared the assays using samples from cancer patients. Paired blood samples were obtained from patients with metastatic cancer under the University of Washington (UW) IRB. Samples were processed by UW using the CellSearch® assay and the AC/CF assay was performed in parallel by RareCyte using AC/CF. RareCyte was blinded to CellSearch® counts until after AC/CF analysis was performed and documented. On average the AC/CF System found 34% more CTCs in 17 prostate cancer patients, 47% more in 15 breast cancer patients, and 70% more in 8 lung cancer patients. In samples where there was more than a 10% difference in CTC count, AC/CF detected >60% more cells with these combined indications. Very low EpCAM expression was confirmed in CTCs from several of the patients where the AC/CF system found greater numbers of cells. These results demonstrate that the AC/CF platform is capable of high CTC recoveries in clinical sa