The role of circulating tumor cells in metastatic breast cancer: prognostic and predictive value.

The aim of the current study was to assess the prognostic value of circulating tumor cells (CTCs) and their related markers at different points of chemotherapy regimens in metastatic breast cancer (MBC) patients. The impact of CTCs on progression free survival (PFS) and overall survival (OS) rates were also assessed. Peripheral blood samples were obtained from 66 female patients with MBC at different time intervals for evaluation of CTCs by flow cytometry (FC). cytokeratin 19 (CK19), mammaglobin, prolactin inducible peptide (PIP), aldehyde dehydrogenase 1 (ALDH1) and human chorionic gonadotropin (hCG) were also assessed by qRT-PCR. Analysis of different CTC levels (at 4, 5, and 6 cells/7 ml), showed statistically significant values at 4 cells/7 ml blood. The presence of baseline CTCs < 4 cells/7 ml, associated significantly with higher PFS (P value = 0.03). Patients showing a decrease in the CTCs level after treatment had significantly prolonged median PFS and OS rates compared to those whose CTCs level increased (P = 0.007 and P = 0.014; respectively). Mammaglobin, CK19, PIP, ALDH1 and hCG expression did not affect PFS or OS. However, patients with CTCs ≥ 4 at diagnosis had higher rates of progression compared to those with CTCs < 4 (1.9 times, P = 0.07), and who metastasized before 4 years showed a worse decrease outcomes (they were 2.4 time more progressed than those who metastasized after 4 years; P = 0.029). CTCs could be an independent prognostic and predictive biomarker for MBC patients' outcomes. Although none of the assessed genes (mammaglobin, CK19, PIP, ALDH1 and hCG) showed correlation with PFS or OS rates, further studies on a larger number of patients are required to validate the current results.