Circulating tumor cells in metastatic breast cancer: clinical relevance and biological potential.

PURPOSE OF REVIEW: The possibility of tumor dissemination through the blood system has been known for years. Circulating tumor cells (CTCs) are detectable in the peripheral blood of patients with early as well as metastatic breast cancer. The prognostic relevance of this biomarker has already been described. By the use of repeated blood sampling along the course of disease, CTCs can be monitored in terms of a regular 'liquid biopsy'. This review aims to summarize recent research findings and actual ongoing clinical studies to demonstrate the actual and future relevance of CTCs in daily clinical routine.

RECENT FINDINGS: Recent research results show that additional molecular analysis of CTCs might be helpful in gaining information about tumor characteristics, tumor heterogeneity and possible therapy resistance. Repetitive invasive core biopsies might be avoided.

SUMMARY: The assessment of molecular attributes may be indispensable for obtaining an optimized and personalized therapy aiming at extended survival and/or improved quality of life.