Avastin More Likely to Cause Blood Clots in Veins, Study SaysNov 19, 2008 | Parker Waichman LLP
Avastin, Genentech's popular cancer drug, has been linked to an increased risk of blood clots in the veins by a new study. According to an article published in the Journal American Medical Association, when Avastin was used with chemotherapy, the risk of such blood clots increased by about a third.
Avastin was approved by the Food & Drug Administration (FDA) in 2004 to treat colon cancer, and in 2006, the agency approved it as a treatment for non-small cell lung cancer. Earlier this year, the FDA approved Avastin as a breast cancer treatment. Avastin was the first approved therapy designed to inhibit angiogenesis, the process by which new blood vessels develop and carry vital nutrients to a tumor. Avastin has been a blockbuster for Genentech, and its parent company Roche AG. For the first nine months of 2007, US sales of Avastin topped $1 billion, accounting for 27% of Genentech’s overall product sales.
When the FDA approved Avastin for breast cancer patients earlier this year, it did so against the recommendation of its own advisory panel. In late 2007, the panel voted 5-4 to recommend that the agency reject Genentech’s application to expand the approved uses of the drug to include advanced breast cancer. The FDA advisory panel vote came after agency staffers posted documents on the FDA website noting that while Avastin did extend the period prior to patients’ breast cancer becoming worse, treatment with the drug did not markedly increase survival time. The FDA documents also pointed out that Avastin caused serious side effects, including cardiovascular problems, bowel perforations, and a few deaths. The FDA staff said that those side effects included several patient deaths that were “probably or definitely” due to Avastin.
This new Avastin study, conducted by researchers at Stony Brook University Cancer Center in New York, consisted of an analysis of 15 clinical trials involving nearly 8,000 patients. The analysis showed that about 12 percent of people who take Avastin developed blood clots in the veins, a rate that's about 30 percent higher than among other cancer patients who are not taking it.
These types of blood clots put patients at a higher risk of death, because they can travel to the lungs. Clots are already a common problem faced by cancer patients.
Dr. Shenhong Wu, coauthor of the Avastin study, told USAToday that the drug should bear the FDA's strongest warning - a black box - regarding its blood clot risk. Doctors didn't know the magnitude of Avastin's risks until now because earlier studies were too small to show a clear trend, Wu said.