Molecularly Targeted Drug Slows Tumor Growth In Patients

Tumor growth slowed considerably in trial patients who were given a high dose of bevacizumab. The time it took for the cancer to show measurable growth was two and a half times longer in these patients compared to those who did not receive the drug (approximately five vs. two months). Although the difference was small, it was highly statistically significant. There was also a smaller, but still significant, effect from the lower dose of bevacizumab.

Kidney cancer is diagnosed in more than 30,000 people each year in the United States. In this phase II trial, 116 patients with advanced cancer and no known effective treatment options were randomly selected to receive placebo (no drug), a low dose of the drug (3 mg/kg), or a high dose (10 mg/kg). Because only minimal side effects were associated with the drug, researchers were able to design a double-blind trial, in which neither patients nor physicians knew which treatment was being given. This rigorous trial design greatly reduces biased results.

Like other molecularly targeted drugs, bevacizumab is designed to specifically interfere with a biological process that promotes tumor growth or survival. This drug targets the angiogenic process -- the growth of new blood vessels that provide a supply of oxygen and nutrients that are necessary for a growing tumor. Bevacizumab is an antibody that neutralizes the vascular endothelial growth factor (VEGF) protein, one of many proteins secreted by tumor cells to promote the development of a new network of blood vessels. By binding to VEGF, bevacizumab prevents it from triggering blood vessel growth, thereby inhibiting tumor growth.

"The results of this trial are encouraging, demonstrating that anti-angiogenic drugs can inhibit tumor growth in patients," said James C. Yang, M.D., of NCI's Center for Cancer Research, the lead investigator on the study. "This is an important first step toward validating, in patients with cancer, the exciting advances in angiogenesis we have seen in the laboratory. We must continue to build on this finding in order to meaningfully prolong the lives of patients with advanced cancer."

More than 20 additional clinical trials are currently underway to evaluate bevacizumab as a treatment for various types of cancer. The drug is being tested in phase III trials for breast and colorectal cancer. Phase II trials with bevacizumab include those for prostate, breast, colorectal, cervical, ovarian, pancreatic, and lung cancers, as well as for mesothelioma and several types of leukemia.

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