Abstract 2285: Comparison of the nCyte Dx and CellSearch systems for CTC enumeration
Authors: Andrade Josefa , Mohl Ramsey , Thomas Stephanie , Kearney John , Bernard Phillip , Sloane Hillary S. 
Published: August 2019

Abstract
Introduction: Circulating Tumor Cells (CTCs) have clinical utility for cancer prognosis and monitoring disease. The goal of this study was to compare CTC enumeration by the FDA-approved CellSearch technology to a new technology, the nCyte Dx system by Axon Dx, LLC.
Methods: Duplicate peripheral blood samples from 24 patients with advanced prostate cancer were collected in CellSave tubes as standard of care and submitted for CTC quantification using the CellSearch system at ARUP Laboratories. Following CellSearch testing, a paired sample was sent from ARUP to Axon Dx for nCyte Dx analyses. For every pair of samples, the blood was collected at the same time, but the sample tested by Axon Dx was aged 24 to 72 hours beyond the sample tested with CellSearch. CellSearch identifies CTCs by immunomagnetic capture of EpCAM-postive cells, while nCyte Dx does not incorporate specific CTC enrichment. With nCyte Dx, all PBMCs are isolated via density-based separation in a CPT tube and stained with Axon’s immunofluorescent cocktail (nPac). The cells are drawn down onto semi-porous membranes and placed onto microscope slides. Slides are imaged with the nCyte, a rapid fluorescent scanning instrument, and Axon’s advanced cell finding and analysis software (nAble) facilitates automated CTC detection. Due to the high-quality optical properties of the nCyte, the detected material can be characterized and categorized based on morphology and cellular structure.
Results: CellSearch-derived CTC counts were compared with the enumeration results from the nCyte Dx system. Results were reported per 7.5mL blood for both methods. Bland-Altman analysis demonstrates that CellSearch and nCyte Dx results agreed in 22 of the 24 patient sample sets tested within a 95% confidence interval (CI). For both discrepant samples, the CellSearch count was found to be higher. The nCyte Dx method generally detected more CTCs than CellSearch in the lower enumeration range (&lt;10 CTCs). Because previous data from Axon Dx shows no CTCs detected in healthy patients, this finding may be attributable to increased sensitivity rather than decreased specificity. Differences between the results may also be attributable to the natural variation between duplicate blood draws, best characterized by the Poisson distribution model.
Summary and Conclusions: A comparison of CTC enumeration results using the CellSearch and nCyte Dx platforms was performed using duplicate blood samples from 24 prostate cancer patients. The results reveal high similarity between the two technologies, with 22 of 24 patients (92%) having enumeration results that agreed within a 95% CI. While both technologies deliver similar results, there are notable advantages of the nCyte Dx system over CellSearch, including a lack of bias toward EpCAM positive material. Additionally, the superior image quality of nCyte Dx may limit subjectivity in CTC identification and offer the ability to characterize CTC heterogeneity.
Citation Format: Josefa Andrade, Ramsey Mohl, Stephanie Thomas, John Kearney, Phillip Bernard, Hillary S. Sloane. Comparison of the nCyte Dx and CellSearch systems for CTC enumeration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2285.