Clinical relevance of circulating CK-19mRNA-positive tumor cells at first diagnosis in patients with metastatic breast cancer.

Abstract

10553 Background: To investigate the clinical relevance of CK-19mRNA-positive CTCs detected before the initiation of front-line treatment in patients with metastatic breast cancer (MBC). Methods: A total of 300 patients with MBC (training set: 200 patients; validation set: 100 patients) at first diagnosis were enrolled. The presence of CK-19 mRNA-positive CTCs was assessed by real-time reverse transcriptase polymerase chain reaction before any systemic treatment. Interaction with known prognostic factors and association of CTCs with clinical outcome were investigated. Results: CK-19 mRNA-positive cells were detected in 139 (69.5%) and 62 (62%) patients of the training and validation set, respectively. There was no association between the detection of CK-19 mRNA-positive CTCs and other clinico-pathological parameters, the tumor burden or the achievement of objective response in either set. The median PFS was significantly lower in patients with detectable CK-19 mRNA-positive CTCs compared to patients without detectable CTCs both in the training (9.0mo vs 12.0mo, respectively; p=0.018) and the validation (10.0mo vs 12.5mo, respectively; p=0.010) set. Similarly, the median OS was significantly higher in patients without detectable CK-19 mRNA-positive CTCs compared to patients with detectable CTCs both sets (training set: 41.4mo vs 29.9mo, respectively, p=0.014; validation set: 46.0mo vs 29.9mo, respectively, p=0.022). Multivariate analysis including all patients (n=300) demonstrated that ER status (HR=1.483; 95% CI: 1.140-1.928) and detection of CTCs (HR=1.440; 95% CI: 1.440-1.913) were independently associated with a decreased PFS and OS (ER status: HR=1.510, 95% CI: 1.085-2.113; detection of CTCs: HR=1.656, 95% CI: 1.148-2.390). Conclusions: These data indicate that the detection of CK-19 mRNA-positive CTCs in patients with MBC at first diagnosis defines a subgroup of patients with dismal clinical outcome.