Genomic of circulating tumor cells in metastatic breast cancer

Abstract

1002 Background: Metastatic breast cancer (MBC) is an incurable condition and palliative treatments are selected by considering pre-treatment prognostic and predictive factors. Recently, we reported the detection of CTCs to be predictive of prognosis and treatment efficacy and reasoned they might also be used to assess biological characteristics of the patient’s tumor to improve on treatment selection. Methods: Twenty patients with newly diagnosed MBC were enrolled in a prospective clinical trial designed to assess the baseline value of CTCs, evaluate the expression of selected genes in CTCs, and compare the expression of same biomarkers in the primary tumor (PT) and/or metastatic site (MS), as determined by standard IHC and FISH. CTCs were assessed by CellSearch, and subjected to real-time PCR (qPCR) for the expression of transcripts for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor (HER-2), notch-1, and mammaglobin (MGB) using commercial primers. Results: Sixteen of patients had =1CTCs. With respect to biomarkers of PT, 17 were ER+, 11 PR+, and 3 HER-2 amplified. Among the 15 patients with MS, the biomarkers were as follows: 9 ER+, 7 PR+, and 2 HER-2 amplified. There were significant associations between the primary and metastatic tumors with respect to the presence of ER (χ2 = 6.516, P = 0.0107), PR (χ2 = 5.529, P = 0.0187), and HER-2 (χ2 = 3.938, P = 0.0472). The qPCR of CTCs detected transcripts: ER in 3 patients (15%); PR in none (0%); MGB and HER-2 in 2 (10%) and 11 patients (55%), respectively. Notch-1 transcripts were detected in 13 patients (65%). CTCs with detectable transcripts of HER-2 were more likely to co-express notch-1 transcripts (χ2 = 4.295, P = 0.038). Of the 4 samples without detectable CTCs, one was HER-2 positive, and three had notch- 1 transcripts. Conclusions: This study demonstrated a significant concordance in biomarkers expression between the tumor cells of the primary tumors and the metastatic site. Furthermore, it suggests that CTCs differ significantly from those tumor cells with regards to the expression of hormone-receptor and HER-2 status. Thus, CTCs may represent a unique and heterogeneous cell population which phenotype and “homing” properties should be further investigated. [Table: see text]