A glioma is a brain tumor that arises from glial cells, the structural cells that surround and support the neurons that do the actual work of the brain. Aggressive gliomas, also called glioblastomas, of the type suffered by Sen. Edward M. Kennedy strike about 9,000 Americans every year, accounting for about a third of all primary brain tumors.
With standard treatments, the median survival is 15 months, according to Dr. Keith L. Black, chairman of the department of neurosurgery at Cedars-Sinai Medical Center in Los Angeles. Two years after diagnosis, about 8% of patients are still alive.
"Age is a very strong predictor of prognosis," Black said, and because Kennedy is 76, his outlook is not as good as that of someone younger.
Unlike most other types of cancer, brain tumors do not metastasize and spread to other organs. But the most aggressive ones, like Kennedy's, spread rapidly throughout the brain, taking up substantial space inside the skull, squeezing other tissue in the brain and impairing its function.
One common course of therapy is administering steroids to reduce swelling and ease the pressure on neurons. But those steroids have many side effects that produce behavioral problems and make sleep difficult, said Dr. Behnam Badie, head of the brain tumor program at City of Hope Comprehensive Cancer Center in Duarte.
Standard treatment involves surgery, radiation and chemotherapy. Surgery entails removing the tumor, but that may not be a good option for Kennedy because his tumor is in the left parietal lobe, which controls language functions, such as the ability to comprehend speech.
This type of tumor sometimes crosses the corpus callosum, which connects the hemispheres of the brain. Surgery is even more difficult in such cases, Black said.
If the tumor is in the language areas of the brain, he said, surgeons will sometimes try to remove it while the patient is conscious so that they can monitor speech function during the procedure.
Dr. Lynne Taylor, a neuro-oncologist at the University of Washington and a spokeswoman for the American Academy of Neurology, noted that surgical resection of brain tumors was usually done in conjunction with the needle biopsy like that performed on Kennedy. The fact that they did not do so suggested that surgery is not possible, she said.
Radiation is similar to having a brain X-ray and is typically given once a day, five days a week, for seven weeks.
Chemotherapy usually involves the drug Temodar. It is given orally and has few side effects. Temodar is one of the few anti-cancer drugs able to cross the blood-brain barrier -- which protects the brain from toxins and other chemicals in the blood -- to reach the tumor, Badie said.
New treatments are also being studied. One experimental approach is to use the drug Avastin, which blocks the formation of new blood vessels that supply the tumor with nutrients. The drug has so far been approved only to treat colon, breast and lung cancer.
According to Black, about 60% of glioma patients who receive Avastin show a benefit on an MRI scan. "We believe it improves survival, and it definitely improves the quality of life," he said.
But, Taylor added, "there are some problems associated with it that we did not expect to see, and there are not very many places where it is being used as front-line therapy."
Another approach, originally developed by Black, involves the use of therapeutic vaccines. Gliomas are not recognized by the patient's immune system, so the body never mounts a defense against them.
Black developed a technique to remove proteins from the tumor and attach them to a form of white blood cell called an antigen-presenting cell, which is then injected back into the patient to activate the immune system.
In phase II studies of the vaccine, which are nearly complete, survival after two years increased from 8% to 42%, he said. Oncologists at Massachusetts General Hospital have a protocol for producing the vaccine, he added.
Preparing the vaccine, however, requires proteins from the tumor. If surgeons were unable to excise any of the tumor, then they would not be able to prepare a vaccine, Taylor said.