Circulating tumour cells in peripheral blood: potential impact on breast cancer outcome

Exosomal miRNA profile as complementary tool in the diagnostic and prediction of treatment response in localized breast cancer under neoadjuvant chemotherapy

BACKGROUND

Breast cancer patients under neoadjuvant chemotherapy includes a heterogeneous group of patients who eventually develop distal disease, not detectable by current methods. We propose the use of exosomal miRNAs and circulating tumor cells as diagnostic and predictive biomarkers in these patients.

METHODS

Fifty-three breast cancer women initially diagnosed with localized breast cancer under neoadjuvant chemotherapy were prospectively enrolled in this study. However, six of them were later re-evaluated and diagnosed as metastatic breast cancer patients by PET-CT scan. Additionally, eight healthy donors were included. Circulating tumor cells and serum exosomal miRNAs were isolated from blood samples before and at the middle of neoadjuvant therapy and exosomal miRNA levels analyzed by qPCR.

RESULTS

Before neoadjuvant therapy, exosomal miRNA-21 and 105 expression levels were higher in metastatic versus non-metastatic patients and healthy donors. Likewise, higher levels of miRNA-222 were observed in basal-like (p = 0.037) and in luminal B versus luminal A (p = 0.0145) tumor subtypes. Exosomal miRNA-222 levels correlated with clinical and pathological variables such as progesterone receptor status (p = 0.017) and Ki67 (p = 0.05). During neoadjuvant treatment, exosomal miRNA-21 expression levels directly correlated with tumor size (p = 0.039) and inversely with Ki67 expression (p = 0.031). Finally, higher levels of exosomal miRNA-21, miRNA-222, and miRNA-155 were significantly associated with the presence of circulating tumor cells.

CONCLUSION

Liquid biopsies based on exosomal miRNAs and circulating tumor cells can be a complementary clinical tool for improving breast cancer diagnosis and prognosis.

Meta-analysis of the prognostic value of circulating tumor cells in breast cancer

PURPOSE

The prognostic value of circulating tumor cells (CTC) detected in breast cancer patients is currently under debate. Different time points of blood collections and various CTC assays have been used in the past decades. Here, we conducted the first comprehensive meta-analysis of published literature on the prognostic relevance of CTC, including patients with early and advanced disease.

EXPERIMENTAL DESIGN

A comprehensive search for articles published between January 1990 and January 2012 was conducted; reviews of each study were conducted and data were extracted. The main outcomes analyzed were overall survival (OS) and disease-free survival (DFS) in early-stage breast cancer patients, as well as progression-free survival (PFS) and OS in metastatic breast cancer patients. Pooled hazard ratio (HR) and 95% confidence intervals (CIs) were calculated using the random and the fixed-effects models. Subgroup and sensitivity analyses were also conducted.

RESULTS

Forty-nine eligible studies enrolling 6,825 patients were identified. The presence of CTC was significantly associated with shorter survival in the total population. The prognostic value of CTC was significant in both early (DFS: HR, 2.86; 95% CI, 2.19-3.75; OS: HR, 2.78; 95% CI, 2.22-3.48) and metastatic breast cancer (PFS: HR, 1.78; 95% CI, 1.52-2.09; OS: HR, 2.33; 95% CI, 2.09-2.60). Further subgroup analyses showed that our results were stable irrespective of the CTC detection method and time point of blood withdrawal.

CONCLUSION

Our present meta-analysis indicates that the detection of CTC is a stable prognosticator in patients with early-stage and metastatic breast cancer. Further studies are required to explore the clinical utility of CTC in breast cancer.

Dynamics of circulating tumor cells in early breast cancer under neoadjuvant therapy

At present, the majority of patients with breast cancer are diagnosed at early stages of disease development. However, a considerable number of such cases develop secondary malignancies after a relatively short period of time. The presence of circulating tumor cells (CTCs) has been proposed as a strong biomarker to predict disease recurrence in metastatic breast cancer. However, the prognostic significance is not clear in early breast cancer. We present results on CTC determination in peripheral blood in non-metastatic breast cancer patients in the context of neoadjuvant treatment. Twenty-six breast cancer patients, scheduled for neoadjuvant therapy, were enrolled in a prospective study, of which 24 were able to complete therapy. CTC assessment was performed by sorting out cytokeratin-positive cells from 10 ml of peripheral blood using immunomagnetic separation, followed by immunocytochemical characterization of cells. Seventeen blood samples out of 24 patients were CTC-positive when collected prior to neoadjuvant chemotherapy. No significant correlations were found between the presence of CTCs and lymph node status (p=0.1), histological type (p=0.802), stage (p=0.43) or overall survival (OS) (p=0.599). Thirteen CTC-positive samples were observed in blood samples collected after treatment. Univariate analyses revealed that the presence of CTCs was related to OS when the detection was positive both before and after treatment (p=0.023). CTCs can be a strong prognostic marker in early breast cancer. The persistence of CTCs before and after treatment can identify a subpopulation of patients with an increased risk of recurrence.