An international Phase III clinical trial has demonstrated that the addition of bevacizumab (Avastin®) to standard oxaliplatin-based chemotherapy improves progression-free survival for patients with previously untreated metastatic colorectal cancer, although the improvement was more modest than had been expected. Memorial Sloan-Kettering Cancer Center medical oncologist Leonard B. Saltz, lead US investigator for the study, presented the findings at the 2007 Gastrointestinal Cancers Symposium, which was co-sponsored by several leading oncology groups.
In the study, which involved 1,401 patients, researchers found that the median progression-free survival (defined as the time from study entry until either tumor growth or patient death) for patients receiving first-line oxaliplatin-based chemotherapy and bevacizumab was 9.4 months versus 8.0 months for patients receiving chemotherapy alone. Based on previous trials with bevacizumab, more substantial benefit had been expected.
"Oxaliplatin-based chemotherapy plus bevacizumab has de facto become the most widely used treatment in the US for metastatic colorectal cancer. But this is the first study to formally examine this practice," said Dr. Saltz. "These data do support its continued use in standard care but also show us that, while bevacizumab is a step forward, it is only a modest step forward, and we have a long way to go."
Bevacizumab is a monoclonal antibody that blocks a protein that allows blood vessels to grow and supply a tumor. It is currently approved for colorectal and lung cancers, and is being tested in other cancers.
Antibodies are proteins made by the immune system to recognize and eliminate foreign substances (antigens). Monoclonal antibodies are antibodies produced in a laboratory and can be tailored to target very specific antigens.
Dr. Saltz is also investigating the use of several other monoclonal antibodies, alone and in combination, that target a variety of proteins critical to tumor cell growth, to treat metastatic colorectal cancer.
