A comprehensive comparison of circulating tumor cell capturing technologies by apheresis of cancer patients.

Abstract

e21017 Background: Obtaining tumor tissue from cancer patients for diagnosis and biomarker assessment for patient selection is challenging. Circulating tumor cells (CTCs) may represent an attractive alternative as a “liquid biopsy”. However, capturing these rare cells from whole blood is a major challenge that still needs significant improvement. Here we present preliminary data of an ongoing study comparing different CTC capturing technologies. Methods: A collaboration network between Bayer Pharma AG, the University of Düsseldorf as clinical partner and providers of CTC capture methods was established. In addition logistics were organised to guarantee a fast and reliable sample transfer. For optimal comparison, CTC preparations from the same patient were used. The required high amounts of sample aliquots and CTCs was obtained by apheresis. Breast and pancreatic cancer patients (non- and metastatic) were enrolled. Blood samples were obtained, as well as buffy coat by apheresis. Samples were shipped within 48 h to partner companies for CTC analysis. At two sites the CellSearch system by Veridex was performed. Today’s standard was compared with another antigen-based method, a filter method and an approach depending on electrophysiological properties. Downstream analysis of the isolated CTCs was performed at Prometheus using their sensitive immunoassay. Results: Significantly higher CTC amounts were detected in buffy coats obtained by apheresis in comparison with CTC counts obtained from a blood draw. In contrast to the blood samples, all methods were able to detect CTCs in buffy coats from both non-metastatic and metastatic cancer patients. The included novel approaches showed in general a better yield of CTCs in comparison to CellSearch. Downstream analysis revealed individual signalling pathway activity profiles. Conclusions: Apheresis is a suitable procedure to capture high amounts of CTCs and therefore to enable an optimal technology comparison. The isolated CTCs are viable and stimulatable. The preliminary results of our study show that an improvement in CTC capturing is taken place, indicating an important step forward regarding the use of CTCs as “liquid biopsy” in a clinical setting.