Durham, N.C. — A drug recently approved by the Food and Drug Administration could prolong the lives of the nearly 1,000 Americans diagnosed annually with malignant brain tumors, many of whom don't live more than six months.

Michael Gressman realized something was wrong with him when he started feeling dizzy and having headaches while training for an Iron Man competition last year.

"My times were getting slower and slower, and at this time of training, I should be going faster and faster," Gressman said.

A computed tomography scan revealed that Gressman had a stage 4 glioblastoma brain tumor. Surgery removed 95 percent of the tumor, but his life expectancy was no more than a year.

Then Gressman joined a trial fro the drug Avastin at Duke University Hospital.

Some tumors, including glioblastomas, depend on a growth factor called VEGF, a protein that stimulates abnormal blood vessels that feed the tumor.

Avastin blocks VEGF – and shrinks brain tumors in more patients and for longer than ever seen in a clinical trial for a brain cancer drug.

"I think it's the largest advance in neuro-oncology in the treatment of brain tumors in the last 30 years," said Dr. James Vredenburgh, an oncologist with Duke.

Avastin had approval for use in some other cancers, but the FDA was concerned about the risk of bleeding for brain tumor patients. However, in the recent trials, bleeding has not been a problem.

"I've noticed a significant difference, and I've been very fortunate," Gressman said. "I've had very few side effects whatsoever."

Gressman has felt well enough to start training with his brother, Eric, for another Iron Man event in August.

Avastin costs about $26,000 for 20 minutes of intravenous treatment. FDA approval of the drug, though, could lead to more insurance companies helping to cover the costs.