Bevacizumab, known by its brand name Avastin, is a type of targeted cancer medication. It is a monoclonal antibody, a man-made protein designed to mimic natural antibodies. Administered as an intravenous infusion, Avastin treats various cancers by interfering with processes that support tumor growth.
Mechanism of Avastin
Avastin works by targeting Vascular Endothelial Growth Factor (VEGF). Tumors require a robust blood supply for growth and spread. Cancer cells secrete VEGF, which promotes the formation of new blood vessels, a process known as angiogenesis.
Avastin binds to VEGF, preventing it from interacting with receptors on endothelial cells that line blood vessels. This halts the signaling for new blood vessel formation. By inhibiting VEGF, Avastin starves the tumor, slowing its growth.
Avastin’s History in Breast Cancer
Avastin received accelerated approval from the U.S. Food and Drug Administration (FDA) in February 2008 for metastatic breast cancer. This approval was based on preliminary studies indicating an increase in progression-free survival, meaning the time patients lived without their cancer worsening. However, this initial approval was conditional, requiring further studies to confirm a significant clinical benefit.
Subsequent clinical trials and a re-evaluation by an FDA advisory panel in July 2010 raised concerns about Avastin’s effectiveness for metastatic breast cancer. These studies did not demonstrate a significant improvement in overall survival, and the observed progression-free survival benefit was often less than three months. The advisory panel recommended removing the breast cancer indication.
In November 2011, the FDA announced the withdrawal of Avastin’s approval for metastatic breast cancer. The decision was based on the conclusion that the drug had not been shown to be safe and effective for this indication, as the benefits did not outweigh the risks. While some patients may have experienced benefits, a clear overall survival advantage was not demonstrated in the confirmatory trials. Despite this withdrawal for breast cancer, Avastin continues to be approved for other cancers, including colorectal, lung, kidney, ovarian, and cervical cancers, where its benefits are more clearly established.
Potential Side Effects
Avastin, like many cancer treatments, can cause a range of side effects, some of which are serious. Common side effects include hypertension, or high blood pressure. Nosebleeds are also a frequent occurrence, as Avastin can reduce platelet counts, affecting the blood’s ability to clot.
More serious side effects can include gastrointestinal perforations, which are holes that develop in the stomach or intestine wall, and impaired wound healing. Bleeding events can range from minor issues like gum bleeding to severe or even fatal hemorrhages. Other potential serious adverse events include proteinuria, indicating kidney issues, and rare neurological disorders such as posterior reversible encephalopathy syndrome (PRES) characterized by brain swelling. Infusion-related reactions, presenting with symptoms like sweating, chills, chest pain, or headache, can also occur during or shortly after administration.
Current Treatment Approaches for Breast Cancer
Current breast cancer treatments are multifaceted and tailored to the individual patient, considering cancer type and stage. These approaches often involve a combination of therapies, including surgery to remove the tumor, followed by radiation therapy to target any remaining cancer cells in the breast area. Systemic treatments like chemotherapy, hormone therapy, and targeted therapies are frequently used to address cancer cells throughout the body, particularly in cases of metastatic disease.
Chemotherapy employs powerful drugs to shrink or destroy cancer cells, while hormone therapy blocks hormones that fuel the growth of hormone receptor-positive breast cancers. Targeted therapies, distinct from Avastin’s anti-angiogenic mechanism, focus on specific proteins or pathways involved in cancer cell growth and survival. While Avastin is no longer a primary treatment for breast cancer, other targeted therapies continue to be developed and utilized in various cancer contexts.