Comparing Sequential Steps For Detection Of Circulating Tumor Cells: More Specific Or Just Less Sensitive?

Abstract

Abstract Background: We compared two surface epithelialantigen (EpCAM)-based approaches for the detectionof breast cancer cells present in the circulation.Methods: Blood from 20 breast cancer patients wasdrawn into standard blood collection tubes (SBCT) andof 7 of these additionally into CellSave® tubes. Aftererythrocyte lysis of the samples from both systems,cells were stained with FITC-anti-EpCAM andpropidium iodide, quantified with an automatedmicroscope and intact cells counted.Results: EpCAM-positive events from 1ml of bloodranged between 2051 and 28875/ml and from SBCT(MAINTRAC® approach) as compared to between 97and 2343/ml from the CellSave® tubes, indicating amore than 10-fold reduction in EpCAM accessibility bythe preservative. Duplicate cell preparations showed ahigh correlation of R2=0.89 (MAINTRAC®) from SBCTvs. a moderate correlation of R2=0.81 from CellSave®tubes, but a good correlation (R2=0.91) between theevents detected from both systems.Between 1/2 and 1/5 of the positive events were viablecells in the MAINTRAC® approach with unequivocalmorphology, and a good (R2=0.89) correlation to totalevents; by contrast, 1/10 to less than 1/100 of theevents in the CellSave® tubes were perhaps cells withequivocal morphology no correlation to total eventsmost positive events being non-recognizable cells. Still30 to 100-fold more cells were recovered than with theCellTrack® Analyzer.Conclusions: The approach without fixative detectsconsiderably more EpCAM-positive events with goodcell morphology as compared to the CellSave®fixation where cell morphology is poor. Magnetic beadenrichment further reduces the number of retrievedcells.