Circulating tumor cells (CTCs) in peripheral blood of primary breast cancer patients

Abstract

10595 Background: Detection of CTCs has been shown to predict decreased PFS and OAS in metastatic breast cancer, whereas only limited data has been published in the adjuvant setting. We evaluate the role of CTCs in peripheral blood at primary diagnosis and during adjuvant chemotherapy, endocrine and bisphophonate treatment within the SUCCESS-Trial (n=3,658 pts). Methods: We analyzed 23ml of peripheral blood from 1767 N+ and high risk N- primary breast cancer pts before systemic treatment. 852 of these pts have undergone follow-up blood sampling after completion of chemotherapy. The presence of CTCs was assessed with the CellSearchSystem (Veridex, Warren, USA). Briefly, after immunomagnetic enrichment with an anti-Epcam-antibody, cells were labelled with anti-cytokeratin (8,18,19) and anti-CD45 antibodies to distinguish epithelial cells and leukocytes. Results: 10% of pts with a blood sampling before systemic treatment (n=170) showed >1CTC before the start of systemic treatment (mean 13, range 2–827). While we found 2 CTCs in 5% of pts, 3% had 3–5 CTCs and 1% 6–10 and >10 CTCs each. The presence of CTCs did not correlate with tumor size (p=.07), grading (p=.30), hormonal status (p=.54) or Her2-Status of the primary tumor (p=.26). However, we observed a significant correlation with the presence of lymph node metastases (p=.015). None of 24 healthy individuals showed more than 1 CTC. Among those 852 pts with follow-up blood sampling after the completion of cytostatic treatment, 11% were CTC positive before starting systemic treatment (mean 7, range 2–166), while 7% of patients presented with >1CTC after completion of chemotherapy (mean 6, range 2–84). Of those, initially CTC positive, 10% remained positive (n=9) and 90% had a negative CTC test after chemotherapy (n=82). Of those initially CTC negative, 93% remained negative (n=711), whereas 7% returned with a positive CTC test (n=50) (p=.24). Conclusions: Our data show good feasibility of this highly standardized and easily applicable approach for the detection of CTCs in a large number of primary breast cancer patients. In a considerable number of patients, persistent CTCs can be detected after completion of cytostatic treatment. Whether this finding is prognostically relevant will have to been shown with longer follow-up of the SUCCESS-trial. No significant financial relationships to disclose.