Abstract P1-01-15: DETECT V - Detection of the expression of estrogen receptor and human epidermal growth factor receptor 2 on circulating tumor cells from metastatic breast cancer patients

Abstract

Abstract Background: The prognostic relevance of circulating tumor cells (CTCs) in metastatic breast cancer (MBC) has constantly been shown in several clinical studies. Nevertheless, the predictive value of CTCs still remains unclear. The DETECT study concept evaluates the impact of CTCs on therapeutic decisions. Patients with hormone-receptor positive, HER2-positive MBC participating in DETECT V are randomized to a dual HER2 targeted therapy (Trastuzumab and Pertuzumab) combined with either endocrine therapy or chemotherapy. Based on the expression of Estrogen Receptor (ER) and Human Epidermal Growth Factor Receptor 2 (HER2) on detected CTCs, an “Endocrine Responsiveness Score (ERS)” is calculated for prediction of endocrine treatment response. Aim of this project was the optimization of staining procedures using immunofluorescence. Methods: CTCs are enumerated and characterized using CELLSEARCH® CXC Kit which is based on the immunomagnetic enrichment of EPCAM-positive cells and immunofluorescent characterization of these cells. Comparison of staining intensities in different cell lines with known expression of ER and HER2 was used to validate the staining protocol. To validate ER-staining, staining intensities of the following cell lines were compared: SKBR-3 (negative control), MCF-7 (positive control) and T47D (intermediate expression). HER2-staining was validated comparing staining intensities of SKBR3 (positive control), MDA-MB 453 (intermediate expression) as well as MCF-7 (negative control). Results: Staining intensities were divided into the following categories: negative, weak, moderate and strong. Signal intensities using CELLSEARCH® system correlated with the known expression of HER2 and ER in the different cell lines. No expression of ER could be shown in SKBR3 cells, T47D cells showed weak expression of ER. MCF-7 cells showed moderate to strong expression of ER but no expression of HER2. MDA-MB 453 and SKBR3 showed moderate to strong and strong expression of HER2, respectively. Expression of HER2 and ER could be depicted accurately using CELLSEARCH® CXC Kit. Results were validated in a ring test in all participating laboratories. First patient samples are currently analyzed. Conclusion: Establishment and validation of the ERS by characterizing CTCs within the framework of the DETECT V study pursues the objective of assessing the potential benefit of endocrine therapy. Validation results and first patient results will be shown. Citation Format: Fehm T, Meier-Stiegen F, Riethdorf S, Schramm A, Polasik A, Niederacher D, Rack B, Taran F-A, Müller V, Janni W, Huober J. DETECT V - Detection of the expression of estrogen receptor and human epidermal growth factor receptor 2 on circulating tumor cells from metastatic breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-01-15.