The government on Thursday approved the first drug that promises to attack cancer by choking off its blood supply, a colon cancer treatment called Avastin.
The drug has only a modest benefit - it can extend the lives of patients with advanced colon cancer by about five months, the Food and Drug Administration cautioned.
But it's a significant development, because Avastin becomes the first drug proved to work according to a novel theory that tumors must form a network of blood vessels to survive - and that shutting down that process, called angiogenesis, could fight cancer in a manner completely differently than other treatments.
That theory was pioneered by Harvard University's Dr. Judah Folkman, who made front-page news in 1998 with reports that his anti-angiogenesis drugs had cured mice of cancer. But attempt after attempt to make such drugs work in people failed.
Indeed, the maker of Avastin, Genentech Inc., saw its stock plummet as recently as 2002 when the drug failed to help breast cancer patients. Then doctors tried Avastin in the sickest of colon cancer patients, those whose cancer has spread to other parts of the body.
In a study of 800 people, half received intravenous Avastin in addition to routine chemotherapy. Not only was tumor growth delayed in those getting Avastin, but the Avastin patients lived about 20 months, five months longer than those getting standard treatment.
In patients that sick, even such a small benefit is considered medically important. It also marked the first time in three decades of research that an anti-angiogenesis drug was proven to help people.
Avastin is a monoclonal antibody, a substance that seeks out and binds to one of the more 20 chemicals known to help tumors' blood vessels grow. The one Avastin targets is called vascular endothelial growth factor, or VEGF.
When Avastin binds to it, VEGF can't stimulate blood vessel growth, thus keeping tumors from growing by denying them nourishing blood.
Avastin occasionally causes some serious side effects, the FDA cautioned. They include formation of holes in the colon that may require surgery to fix, impaired wound healing and internal bleeding.
More common side effects are high blood pressure, fatigue, blood clots, diarrhea, appetite loss and increased risk of infection because of decreased white blood cells.