Predictive Potential of Angiogenic Growth Factors and Circulating Endothelial Cells in Breast Cancer Patients Receiving Metronomic Chemotherapy Plus Bevacizumab

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Abstract
Purpose: The association of chemotherapy and antiangiogenic drugs has shown efficacy in clinical oncology. However, there is a need for biomarkers that allow selection of patients who are likely to benefit from such treatment and are useful for indicating best drug combination and schedule. Experimental Design: We investigated the predictive potential of six angiogenic molecules/transcripts and nine subpopulations of circulating endothelial cells (CEC) and progenitors (CEP) in 46 patients with advanced breast cancer treated with metronomic cyclophosphamide and capecitabine plus bevacizumab. Results: Median time to progression was 281 days. Baseline CECs higher than the first quartile were associated with an increased time to progression (P = 0.021). At progression, CECs were markedly reduced (P = 0.0002). In the cohort of 15 long-term responders, who progressed later than 1 year after beginning of therapy, circulating vascular endothelial growth factor (VEGF)-A levels measured after 2 months of therapy were significantly reduced, and there were significant trends toward lower levels of PDGF-BB, CEPs, and CECs. At the time of progression, angiogenic growth factors VEGF-A and basic fibroblast growth factor were significantly increased. Conclusions: Baseline CECs (likely reflecting an active vascular turnover) predicted a prolonged clinical benefit. At the time of relapse, a pattern of decreased CECs and increased angiogenic growth factors suggested a switch toward a different type of cancer vascularization. VEGF-A and basic fibroblast growth factor levels after 2 months of therapy were also useful to identify patients whose disease was likely to progress. These biomarkers are likely to be useful for treatment selection and might be incorporated in design of future studies. (Clin Cancer Res 2009;15(24):7652–7)