- [Resource Hub](/) - [Publication](/?resource-type=publication#library) - Circulating tumor cell detection: a prospective comparison between CellSearch and Rarecyte platforms in patients with progressive metastatic breast cancer # Circulating tumor cell detection: a prospective comparison between CellSearch and Rarecyte platforms in patients with progressive metastatic breast cancer Dirix L, Buys A, Oeyen S, Peeters D, Liègeois V, Prové A, et al. Breast Cancer Research and Treatment . 2022;193(2):437-444. DOI [10.1007/s10549-022-06585-5](https://doi.org/10.1007/s10549-022-06585-5). PMID 35397078. PMCID PMC9090706. How to cite ### AMA Dirix L, Buys A, Oeyen S, Peeters D, Liègeois V, Prové A, et al. Circulating tumor cell detection: a prospective comparison between CellSearch and Rarecyte platforms in patients with progressive metastatic breast cancer. Breast Cancer Res Treat . 2022;193(2):437-444. doi:10.1007/s10549-022-06585-5 ### APA Dirix, L., Buys, A., Oeyen, S., Peeters, D., Liègeois, V., Prové, A., et al. (2022). Circulating tumor cell detection: a prospective comparison between CellSearch and Rarecyte platforms in patients with progressive metastatic breast cancer. Breast Cancer Research and Treatment , 193(2), 437-444. https://doi.org/10.1007/s10549-022-06585-5 ### BibTeX @article{dirix2022circulating, title = {Circulating tumor cell detection: a prospective comparison between CellSearch and Rarecyte platforms in patients with progressive metastatic breast cancer}, author = {Dirix, Luc and Buys, Andy and Oeyen, Steffy and Peeters, Dieter and Liègeois, Vincent and Prové, Annemie and others}, journal = {Breast Cancer Research and Treatment}, volume = {193}, number = {2}, pages = {437--444}, year = {2022}, doi = {10.1007/s10549-022-06585-5} } Circulating tumor cell counts carry prognostic weight in metastatic breast cancer, but several enumeration platforms exist and direct comparisons between them are scarce. The most widely used method enriches for cells that carry the epithelial antigen EpCAM, which can miss tumor cells that express it only weakly. This study ran paired blood samples from 86 patients with progressive metastatic breast cancer through two platforms in parallel, in two laboratories each blinded to the other's results: an enrichment-free, density-based slide-imaging workflow and the established FDA-cleared reference method. It then asked whether the counts agreed and whether either predicted survival. The two platforms enumerated circulating tumor cells equivalently, their paired counts were strongly correlated, and both separated patients at the validated five-cell threshold. It was the first time prognostic significance had been shown for the density-based platform. [Read publication at Breast Cancer Research and Treatment](https://pmc.ncbi.nlm.nih.gov/articles/PMC9090706/) ## Key findings - The two platforms enumerated circulating tumor cells equivalently across 100 paired samples. At least one CTC was detected in 65% to 75% of samples, both platforms returned a median of 3 CTCs per 7.5 mL of blood, and the paired counts were strongly correlated (Spearman r = 0.823, p ## The AccuCyte–CyteFinder workflow in the methods “For the RareCyte test, a blood sample is collected in a 10 mL AccuCyte® BCT tube (RareCyte, Seattle, USA). 7.5 mL of this blood is transferred into an AccuCyte® Separation Tube. Subsequently, the tube is centrifuged and four layers are identified: plasma on top, then a broad gray layer of platelets, a thin layer of white blood cells (buffy coat), and finally a layer of compacted red blood cells. After centrifugation, the Separation Tube is clamped to create a barrier between the red blood cells and the rest of the sample. Plasma is then removed and replaced with a high density fluid. The buffy coat is retrieved after a second centrifugation. Then, transfer fluid is added to the buffy coat and after 10–60 min of incubation, the sample is applied to charged microscope slides with a spreading device. After drying, slides are processed using the Ventana DISCOVERY ULTRA automated platform. This platform applies fluorescently labeled antibodies against pan-CK and EpCAM, CD45, and a nuclear dye. The stained slides are scanned on a CyteFinder® digital microscope and candidate CTCs are identified using CyteMapper® image analysis software.” — Dirix et al., Breast Cancer Research and Treatment (2022), Methods, “Measurement methods” ## Why it matters for The AccuCyte–CyteFinder workflow users If you are weighing an enrichment-free approach to circulating tumor cells, this study is a useful benchmark. Its central result is equivalence: counts from the AccuCyte–CyteFinder workflow tracked an established FDA-cleared reference method closely across 100 paired samples, and both separated patients at the same five-cell threshold. That distinction matters because the reference method enriches for EpCAM-positive cells before it looks, so a cell that carries little of that antigen can be lost before counting begins. The AccuCyte–CyteFinder workflow instead isolates nucleated cells by density and images them on slides, so the epithelial marker is read after the cells are captured rather than used to select them. For your own work the value is twofold: the workflow reproduced a validated prognostic cut-off head to head with an accepted standard, and it was the first time that threshold carried prognostic weight on this platform. When you need counts you can defend against an established method, showing that the two agree, and that yours also predicts outcome, is what earns a place in the workflow. 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