International study on inter-reader variability for circulating tumor cells in breast cancer

Abstract

IntroductionCirculating tumor cells (CTCs) have been studied in breast cancer with the CellSearch® system. Given the low CTC counts in non-metastatic breast cancer, it is important to evaluate the inter-reader agreement.MethodsCellSearch® images (N = 272) of either CTCs or white blood cells or artifacts from 109 non-metastatic (M0) and 22 metastatic (M1) breast cancer patients from reported studies were sent to 22 readers from 15 academic laboratories and 8 readers from two Veridex laboratories. Each image was scored as No CTC vs CTC HER2- vs CTC HER2+. The 8 Veridex readers were summarized to a Veridex Consensus (VC) to compare each academic reader using % agreement and kappa (κ) statistics. Agreement was compared according to disease stage and CTC counts using the Wilcoxon signed rank test.ResultsFor CTC definition (No CTC vs CTC), the median agreement between academic readers and VC was 92% (range 69 to 97%) with a median κ of 0.83 (range 0.37 to 0.93). Lower agreement was observed in images from M0 (median 91%, range 70 to 96%) compared to M1 (median 98%, range 64 to 100%) patients (P < 0.001) and from M0 and <3CTCs (median 87%, range 66 to 95%) compared to M0 and ≥3CTCs samples (median 95%, range 77 to 99%), (P < 0.001). For CTC HER2 expression (HER2- vs HER2+), the median agreement was 87% (range 51 to 95%) with a median κ of 0.74 (range 0.25 to 0.90).ConclusionsThe inter-reader agreement for CTC definition was high. Reduced agreement was observed in M0 patients with low CTC counts. Continuous training and independent image review are required.

Circulating Tumor Cells and Circulating Tumor DNA: Challenges and Opportunities on the Path to Clinical Utility

“…[19][20][21]. Recent data suggest that this technology can also be used for clinical trials across multiple laboratories in the nonmetastatic setting provided that continuous training and central image review is performed (22).…”

Circulating Tumour Cells as Liquid Biopsy in Breast Cancer—Advancing from Prognostic to Predictive Potential

“…A number of methods exist to enrich blood samples to permit identification, the most widely used of which remains CellSearch® (Veridex, Raritan, NJ) [2]. This process exploits the presence of epithelial cell adhesion molecules (EpCAM) on certain breast cancer cells (but absent on white blood cells) by using an antibody to EpCAM that is bound to small ironcontaining particles.…”

“…Deeper analysis of gene mutation and expression can also be performed on CTCs, especially if they are unharmed in the isolation process, and may also be able to guide treatment selection [2,24]. Many trials in this area are still in the early stages, attempting to demonstrate analytical and clinical validity (proof of concept) before moving onto clinical utility.…”

“…The potential to tailor treatment has been explored in a study of CTC cultures from cells taken from six patients with MBC [2]. The expansion of purified tumour cell populations permitted next-generation sequencing, a process generally not possible on small cell numbers.…”

Circulating Endothelial Cells and Their Subpopulations: Role as Predictive Biomarkers in Antiangiogenic Therapy for Colorectal Cancer

“…37 It allows standardized analyses of CECs in different laboratories 38,39 and shipment of blood samples in special tubes containing preservatives. 40 The generated images are evaluated for CEC content by visual inspection, in which CECs are defined as DAPI (4 0 ,6-diamidino-2-phenylindole) positive, CD105 þ , CD146 þ , and CD45 À .…”