Avastin Efficacy Against Deadly Brain Tumors QuestionedMar 30, 2009 | Parker Waichman LLP
Genentech's rational for fast-track approval of Avastin as a treatment for a deadly type of brain tumor is being questioned by Food & Drug Administration (FDA) staffers. According to the Associated Press, an FDA advisory panel will consider whether or not to approve Avastin as as a treatment for recurring glioblastoma multiforme, a form of brain cancer that is generally fatal within six months, at a meeting tomorrow.
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 was approved by the FDA in 2004 to treat colon cancer, and in 2006, the agency approved it as a treatment for non-small cell lung cancer. Last year, the FDA also approved Avastin as a breast cancer treatment.
Avastin approvals have come with controversy, as the drug has been the subject of various safety concerns. When the FDA approved Avastin for breast cancer patients last year, it did so against the recommendation of its own advisory panel. In late 2007, the panel had 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.
Last June, researchers at Stony Brook University Cancer Center in New York released a study showing that about 12 percent of people who took 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.
In December, Genentech also reported that some Avastin patients had experienced eye inflammation when it was used off-label to treat an eye condition.
According to the Associated Press, Genetech's application for expanded Avastin approval relies on imaging scans that claim to show a reduction in tumor size. Patients were considered responsive to the drug if their tumor shrunk at least 50 percent over the course of two consecutive visits to their physician. Genentech reported that roughly 25 percent and 20 percent of brain cancer patients in two separate studies responded successfully to the drug, the Associated Press said.
But in documents posted online, FDA reviewers said they never rely on response rate when considering a fast-track approval, and noted that measuring tumor size via medical imaging is difficult, the Associated Press said. According to the report, FDA advisors had previously said that Avastin would need to have a response rate above 30 percent to outweigh doubts about imaging.