Identification of high independent prognostic value of nanotechnology based circulating tumor cell enumeration in first-line chemotherapy for metastatic breast cancer patients

Enumeration of circulating tumor cells (CTCs) is a promising tool in the management of metastatic breast cancer (MBC). This study investigated the capturing efficiency and prognostic value of our previously reported peptide-based nanomagnetic CTC isolation system (Pep@MNPs). We counted CTCs in blood samples taken at baseline (n = 102) and later at patients' first clinical evaluation after starting firstline chemotherapy (n = 72) in a cohort of women treated for MBC. Their median follow-up was 16.3 months (range: 9.0-31.0 months). The CTC detection rate was 69.6 % for the baseline samples. Patients with ≤2 CTC/2 ml at baseline had longer median progression-free survival (PFS) than did those with >2 CTC/2 ml (17.0 months vs. 8.0 months; P = 0.002). Patients with ≤2 CTC/2 ml both at baseline and first clinical evaluation had longest PFS (18.2 months) among all patient groups (P = 0.004). Particularly, among patients with stable disease (SD; per imaging evaluation) our assay could identify those with longer PFS (P < 0.001). Patients with >2 CTC/2 ml at baseline were also significantly more likely to suffer liver metastasis (P = 0.010). This study confirmed the prognostic value of Pep@MNPs assays for MBC patients who undergo firstline chemotherapy, and offered extra stratification regarding PFS for patients with SD, and a possible indicator for patients at risk for liver metastasis.