Clinical relevance of circulating CK-19mRNA-positive tumour cells before front-line treatment in patients with metastatic breast cancer

BACKGROUND: To investigate the clinical relevance of CK-19mRNA-positive circulating tumour cells (CTCs) detected before the initiation of front-line treatment in patients with metastatic breast cancer (MBC). METHODS: The presence of CTCs was detected in 298 patients with MBC using a real-time PCR (RT-PCR assay. In 44 patients, the detection of CTCs was evaluated by both the CellSearch and the RT-PCR assay. Interaction with known prognostic factors and association of CTCs with clinical outcome were investigated. RESULTS: There was a strong correlation between the detection of CTCs by both assays. CK-19mRNA-positive CTCs were detected in 201 (67%) patients and their detection was independent of various patients’ clinico-pathological characteristics. The median progression-free survival (PFS; 9.2 vs 11.9 months (mo), P=0.003) and the overall survival (OS; 29.7 vs 38.9 mo, P=0.016) were significantly shorter in patients with detectable CK-19mRNA-positive CTCs compared with patients without detectable CTCs. Multivariate analysis demonstrated that oestrogen receptor status, performance status and detection of CTCs were emerged as independent prognostic factors associated with decreased PFS and OS. CONCLUSION: The detection of CK-19mRNA-positive CTCs in patients with MBC before front-line therapy could define a subgroup of patients with dismal clinical outcome.