P4-07-13: Prognostic Impact of Circulating Tumor Cells Assessed with the Cell Search Assay and Adna Test Breast in Metastatic Breast Cancer Patients – The DETECT Study

Background

Over the last decade circulating tumor cells (CTC) were established as a prognostic factor in breast cancer patients. However, there are very limited studies comparing different test methods, although several are available.The DETECT trial for metastatic breast cancer patients was designed to investiate the prognostic impact of CTC. Here, we report on the prognostic relevance of CTC testing with different detection methods.

Material and Methods: Patients with primary metastatic breast cancer or metastatic recurrence were prospectively enrolled in this multicenter trial. CTC were detected using the FDA-approved Cell Search® assay applying immunocytochemistry and the RNA-based Adna Test Breast Cancer™. After a median follow-up of 11 months the first survival data are now presented.

Results: Both methods could be performed in 221 patients. Using the CellSearch™ assay 116 of 221 patients were CTC-positive based on the cut-off level of 5 cells. Presence of CTC was associated with the site of metastatic disease. The OS was 15.4 months in CTC positive pts. (95%-CI: 13.5−17.1 mths) compared to 20.4 mths. in CTC negative pts. (19.1−21.9 mths.; p<0.001). In the multivariate analysis presence of CTC was the only independent predictor for overall survival (HR: 3.4, 95%-CI: 1.7−6.3) including tumorbiological factors, menopausal status, number and sites of metastatic disease. The progression-free survival was not correlated with CTC status in our cohort receiving different types of systemic treatment (p=0.197). When the AdnaTest Breast was performed, 88 of 221 (40%) patients were CTC positive. Except for HER2 status, no correlation could be observed between CTC positivity and any of the clinicopathological factors. CTC positivity assessed by the AdnaTest Breast has no impact on PFS and OS. A multivariate analysis was therefore not performed.

Conclusions: Currently, several different tests are available for CTC detection. Only a few tests have been approved by the FDA and been validated in large clinical trials. Therfore, it will be important to compare new techniques with the Cell Search assay.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-13.