Window of opportunity: A new insight into sequential bevacizumab and paclitaxel in two cases of metastatic triple-negative breast cancer.

Bevacizumab, an antiangiogenic monoclonal antibody against vascular endothelial growth factor, was designed to normalize tumor vasculature and reduce intratumoral pressure. It can create a 'normalization window' during which the cancer can be attacked the most effectively, and the effects of chemotherapeutic drugs are enhanced. Representative trials (E2100, AVADO, RIBBON-1, RIBBON-2 and TURANDOT) have shown that the addition of bevacizumab to chemotherapy has significant benefits on progression-free survival for metastatic breast cancer, but not on overall survival. The present study describes two patients with metastatic triple-negative breast cancer who received 6 courses of bevacizumab-containing chemotherapy. Each course comprised 5-7.5 mg/kg bevacizumab administered on days 1 and 15, and 20-24 h after bevacizumab delivery, 80 mg/m2 paclitaxel was administered for 3 weeks on days 2, 9 and 16, followed by 1 week of rest. Following sequential treatment with bevacizumab and paclitaxel, the results of computed tomography showed that the tumors were rapidly reduced in size. Based on the imaging findings from three-dimension power Doppler ultrasonography in one of the breast cancer patients who received neoadjuvant chemotherapy with bevacizumab, the possible timing of the normalization window was 20-24 h after the administration of bevacizumab. The normalization window may provide an opportunity to enhance the effect of chemotherapy with the aid of bevacizumab.