Angiogenesis as targeted breast cancer therapy

Neo-angiogenesis appears to be a critical feature of tumor growth, migration, and metastasis. Therefore, inhibition of angiogenesis is an appealing strategy for treatment of cancer. Since angiogenesis is the result of several mechanistic processes, controlled by numerable pro- and anti-angiogenic factors and their receptors, multiple possibilities to prevent or reverse tumor-induced neo-vascularization have been proposed. Of these, currently, the most promising approach has been the use of bevacizumab, a humanized monoclonal antibody directed against the most potent pro-angiogenic factor, vascular endothelial growth factor (VEGF). Bevacizumab has been shown to be active in several malignancies, in particular colo-rectal cancer. Although early studies of bevacizumab in far-advanced metastatic breast cancer were disappointing, the results of a recently reported clinical trial by the Eastern Oncology Group comparing first line paclitaxel with or without bevacizumab has demonstrated statistically significant improvements in response rates and time progression. Ongoing studies are now investigating the benefits of bevacizumab with other chemotherapeutic and biologic agents in early metastatic disease as well as in the adjuvant setting. Other anti-angiogenic agents remain in early clinical trials. Small molecular inhibitors of VEGF receptor tyrosine kinase activity, such as sunitinib, appear promising. Nearly 40 years after it was first proposed, inhibition of angiogenesis appears to be gaining a role in medical oncology.