Improved circulating tumor cell detection by a combined EpCAM and MCAM CellSearch enrichment approach in breast cancer patients undergoing neoadjuvant chemotherapy detection using

Circulating tumor cells (CTCs) are detected by the CellSearch System in 20-25% of primary breast cancer (pBC) patients. To improve CTC detection, we investigated melanoma cell adhesion molecule (MCAM) as enrichment marker next to epithelial cell adhesion molecule (EpCAM) and tested the clinical relevance of MCAM-positive CTCs in patients with HER2-negative stage II/III pBC starting neoadjuvant chemotherapy (NAC) in the NEOZOTAC trial. Using the CellSearch System, EpCAM-positive and MCAM-positive CTCs were separately enriched from 7.5 mL blood, at baseline and after the first NAC cycle. Circulating endothelial cells (CECs) were measured using flow cytometry. Primary objective was to improve the CTC detection rate to ≥40% combining EpCAM/MCAM. Correlations of CTC and CEC counts and pathological complete response (pCR) were also explored. At baseline, we detected EpCAM-positive and MCAM-positive CTCs in 12/68 (18%) and 8/68 (12%) patients, respectively. After one cycle, this was 7/44 (16%) and 7/44 (16%) patients, respectively. The detection rate improved from 18% at baseline and 16% after one cycle with EpCAM to 25% ( P =0.08) and 30% ( P =0.02), respectively, with EpCAM/MCAM. No patients with versus 23% of patients without MCAM-positive CTCs at baseline achieved pCR ( P =0.13). EpCAM-positive CTCs and CEC counts were not correlated to pCR. Combined EpCAM/MCAM CellSearch enrichment thus increased the CTC detection rate in stage II/III pBC. We found no associations of CTC and CEC counts with pCR to NAC. The clinical relevance MCAM-positive CTCs deserves further study. In this study we used an EpCAM/MCAM CellSearch enrichment approach to improve CTC detection in patients with stage II/III breast cancer starting neoadjuvant chemotherapy (NAC). Primary objective was to improve the CTC detection rate from ~20% to 40% of patients. Secondary objectives were to determine baseline CEC counts and changes of CTCs and CECs during NAC, and to investigate associations between the presence and dynamics of EpCAM-positive and MCAM-positive CTCs and CECs with pathological complete response (pCR) to NAC. Standard statistical tests were applied: binomial tests for percentages, Pearson’s Chi-square tests for categorical variables, and Student’s t or Mann-Whitney U tests for continuous variables. Changes in CEC counts were tested by the Wilcoxon signed rank test. Binomial tests were one-sided, all other tests were two-sided. We considered a P <0.05 as statistically significant. Analyses were performed using SPSS 21 (IBM, Armonk, NY, USA).