 Bevicizumab Avatstin is a humanized monoclonal antibody to VEGF. VEGF is known to play a pivotal role in tumor angiogenesis and is a significant mitogenic stimulus for arterial, venous and lymphatic endothelial cells. The addition of bevacizumab to chemotherapy has been shown to increase overall response rate, duration of response and survival for patients with metastatic colon cancer 4 and is beneficial in first line non-small cell lung cancer and metastatic breast cancer 1, 2, and second line metastatic colorectal cancer 7. VEGF signals through phosphoatidylinositol 3-kinase PI3K and Akt as well as through the extracellular regulated kinase ERK 12, a mitogen activated protein kinase MAPK. VEGFs multiple biologic actions may be mediated by different pathways. Erikkson demonstrated that VEGF induced hyperpermeability was highly dependent on activation of the AKT pathway, while the angiogenic effect was largely unaffected by blocking this pathway and likely depended on ERK activation 3. 