Abstract P1-08-21: Detection and monitoring of circulating endothelial cells, circulating tumor cells and disseminated tumor cells during neoadjuvant breast cancer treatment including bevacizumab

Abstract

Abstract Background: Results from studies with bevacizumab in addition to traditional neoadjuvant therapy (NAT) indicate a need for predictive biomarkers. As a sub-study of the NeoAva study (a neoadjuvant study), the aim was to investigate the potential association between the presence of circulating endothelial cells (CECs) in peripheral blood (PB), circulating tumor cells (CTCs) in PB and disseminated tumor cells (DTCs) in bone marrow (BM) at different time points during NAT +/- bevacizumab and at one year follow-up, and therapy response. Patients and methods: A total of 150 HER2-negative patients with cT2-4 (≥ 2.5cm) N0-3 M0 status were randomized to receive NAT with or without bevacizumab. In this sub-study, 90 patients have so far been analyzed. Of these, 82 received chemotherapy (FEC100→taxane) and 8 received endocrine therapy (letrozole) + / - bevacizumab. Therapy response was evaluated according to the RECIST criteria and achievement of pathological complete response (pCR). Number of CECs, CTCs and DTCs were assessed at baseline after 12 weeks, at surgery (after 24 weeks) and at one year follow-up. Blood samples were analyzed by CellSearch® to assess CEC and CTC counts. The detection of DTCs was performed by immunocytochemical analysis of 2 × 106 BM mononuclear cells. Results: The pathological complete response rate was 10 out of 90 (11.1%), eight of these patients received bevacizumab. For bevacizumab-treated patients with a change in CEC counts from baseline to time of surgery below median change (27 CECs), 35% (6/17) achieved pCR compared to 6% (1/18) in the group with a CEC count-increase above median change (p = 0.035). The corresponding pCR rates for patients not receiving bevacizumab (median CEC change 131 CECs) were 0% (0/15) and 13% (2/14), respectively. Stepwise testing of thresholds for CEC changes in the bevacizumab-arm revealed significant associations to pCR for change-values between 20 and 40. CTC- and DTC-status or -changes were not associated with tumor response or CEC changes. Conclusion: The presented results indicate that the level of change in the number of circulating endothelial cells during neoadjuvant therapy including bevacizumab is associated with the pathological complete response rate in breast cancer patients. This supports additional testing of CECs as a surrogate marker for response to this treatment. The analyses will be up-dated with results from the rest of the included patients. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-21.