Circulating Tumor Cells and Bevacizumab Pharmacokinetics during Neoadjuvant Treatment Combining Chemotherapy and Bevacizumab for Early Breast Cancer: Ancillary Analysis of the AVASTEM Trial

We recently published the results of the AVASTEM study, in which we explored the impact of the addition of an angiogenesis inhibitor (bevacizumab) to standard pre-operative chemotherapy for breast cancer. In this work, we aimed to identify biological parameters correlated to prognosis and treatment efficacy. To do so we explored if circulating tumor cells (CTCs), that are cells released by the tumor and that can be detected in the bloodstream of a patient; can predict the outcome of the women treated in this study. We also analyzed if bevacizumab concentration in the blood during treatment was associated with outcome, i.e., response to treatment and survival. We observed that CTCs detection before treatment initiation is associated with survival but was not correlated to local response to treatment. We moreover found that CTC status after three weeks of chemotherapy was not correlated to outcome as well as bevacizumab levels before and during treatment. However, bevacizumab concentration tended to be associated with an increase of hematological toxicities during the study. We thus show in this work that CTCs detection at baseline is prognostic for patients with breast cancer receiving a pre-operative chemotherapy-bevacizumab combination, and that this prognostic value was independent of tumor response.