WASHINGTON (AP) — The Food and Drug Administration will meet later this month to review Genentech's blockbuster cancer drug Avastin for a new use against a form of brain cancer. The agency's panel of outside cancer experts will meet March 31 to assess the safety and effectiveness of the injectable drug for patients with glioblastoma multiforme, the deadliest type of brain tumor. The FDA is not required to follow the advice of its panelists, though it usually does. Avastin is already approved to treat colon and breast cancer, along with the most common form of lung cancer. The drug was Genentech's top-selling product last year with sales of $2.69 billion in U.S. revenue. South San Francisco, Calif.-based Genentech has asked the FDA to approve its application under the accelerated approval program, which grants market access to drugs with promising preliminary results. Companies gain full approval after submitting follow-up studies that confirm their drugs' effectiveness. Roughly 10,000 U.S. patients are affected each year by glioblastoma multiforme, according to the National Cancer Institute. The cancer quickly returns in nearly all patients treated for the disease.