e22117 Background: The detection, enumeration and isolation of circulating tumor cells (CTC) has considerable potential to influence the clinical management of patients with breast cancer. There is however a substantial variability in the rates of positive samples using existing detection techniques. Methods: This study was designed to compare three techniques for detecting CTC in blood of 80 patients with metastatic breast cancer (MBC) and 20 healthy controls: the CellSearch System, which is an automated, standardized and regulatory-approved system for the immunocytochemical detection and quantification of CTC in blood; ii) the AdnaTest Breast Cancer Select/Detect, which involves the detection of tumor-associated transcripts by RT-PCR after an immunomagnetically enrichment of tumor cells; iii) an in-house developed multimarker qRT-PCR assay, which involves the quantification of tumor-associated transcripts (CK-19 and MAM) by qRT- PCR. Results: As a result, 23% of patients with MBC were positive by the CellSearch System (≥5 CTC), 22% by the AdnaTest (>0.30 ng/μl for any of the amplicons), 31% by qRT-PCR for CK-19 and 49% by qRT-PCR for MAM. Samples were more likely to be positive by qRT-PCR for at least one mRNA marker than by the CellSearch System (P<0.001) or the AdnaTest (P <0.001). The concordance between samples analyzed by the CellSearch System and the AdnaTest was substantial (κ = 0.667, P <0.001). Agreement between both detection techniques was observed in 88% of blood samples. When the CellSearch System was compared with the qRT-PCR assays for CK-19 and MAM, we observed agreement percentages of 78% and 58%, respectively (κ = 0.462, P <0.001 and κ = 0.159, P = 0.09). Agreement between the AdnaTest and the qRT-PCR assays for CK-19 and MAM was observed in 78% and 53% of blood samples, respectively (κ = 0.443, P <0.001 and κ = 0.05, P = 0.607). Conclusions: We observed a substantial variation in the detection rates of CTC in blood from MBC patients using three different techniques. A higher rate of positive samples was observed using a combined qRT-PCR approach for CK-19 and MAM, which suggests that this is currently the most sensitive technique for detecting CTC. No significant financial relationships to disclose.
Circulating tumour cell detection: a direct comparison between the CellSearch System, the AdnaTest and CK-19/mammaglobin RT–PCR in patients with metastatic breast cancer
