DETECT V – Detection of estrogen receptor and human epidermal growth factor receptor 2 using CELLSEARCH® CXC kit

Background: The prognostic relevance of the enumeration of circulating tumor cells (CTCs) in metastatic breast cancer (MBC) is well known. 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 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 for the ERS.

Methods: CTCs were 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.

Results: To validate ER-staining, staining intensities of the following cell lines after processing in the CELLSEARCH® were compared: SKBR-3 (negative control), MCF-7 (positive control) and T47D (intermediate expression). HER2-staining was validated comparing staining intensities of SKBR3 and MDA-MB 453 (positive controls), T47D (intermediate expression) as well as MDA-MB 231 and MCF-7 (negative controls). Staining intensities were subdivided into the following categories: negative, weak, moderate and strong. Results were validated in a ring test in all participating laboratories. First patient samples are currently analyzed.

Conclusion: Validation results and first patient results will be shown.