By Rob Stein
Washington Post Staff Writer
Wednesday, May 21, 2008
The kind of cancer that Sen. Edward M. Kennedy is fighting is a common, highly lethal form of brain tumor that is very difficult to treat, experts said yesterday.
About 10,000 cases are diagnosed each year in the United States, and only about half of those patients survive one year, experts said. After two years, perhaps 25 percent are still alive.
"In general, it's a very grim kind of prognosis," said Robert Laureno, chief of neurology at Washington Hospital Center. "It's a bad kind of tumor."
A key question is exactly which kind of malignant glioma Kennedy has -- anaplastic astrocytoma or glioblastoma multiforme, said Lynne Taylor of the Virginia Mason Medical Center in Seattle. Those with anaplastic astrocytoma have a somewhat better prognosis; they survive about three years on average, she said. Doctors will be able to determine what type of tumor Kennedy has by further analysis of a biopsy sample taken at the hospital.
In neither case are the tumors curable, Taylor said: "They always come back."
Most malignant gliomas diagnosed in older people tend to be more aggressive and less treatable, experts said. Kennedy, a Democrat from Massachusetts, is 76.
"Unfortunately, the vast majority -- about 70 percent of those cancers -- in adults over 50 tend to be the much more malignant type that typically lead to death within 12 to 18 months," said Harald Sontheimer, a neurobiologist at the University of Alabama at Birmingham.
The American Cancer Society puts the five-year survival rate for patients older than 45 at 16 percent for those with anaplastic astrocytomas, and 2 percent or less for those with glioblastomas.
Depending on exactly where the tumor is and how big it is, surgeons sometimes try to remove as much as they can. But that is difficult, because the tumor usually has penetrated deep into the brain.
"It tends to infiltrate in all directions. Even when one chooses to operate on one, it's usually impossible to take out. It's usually weaving its way in all directions," Laureno said. "You can't even see the whole thing to take it all out."
The left parietal lobe, where Kennedy's tumor is located, is responsible for a host of crucial functions, including some aspects of speech, as well as sensation and movement on the right side of the body.
"If the tumor is located in very essential parts of the brain, such as those that control speech and motor functions, then trying to perform surgery could leave the patient devastated," said Vivek Deshmukh, director of cerebrovascular neurosurgery at George Washington University.
Regardless of whether patients undergo surgery, they typically receive radiation and chemotherapy to try to shrink the tumor and control its growth. A variety of regimens are used, including a common course that involves seven weeks of targeted radiation treatment combined with an oral drug called Temodar to sensitize the tumor to the therapy, Taylor said. That is followed by five days of the drug every month for as long as it appears to be effective.
"The lucky patients continue for two years if it's working," Taylor said. "If you relapse within months, the enthusiasm to do more is obviously less."
Although a variety of experimental therapies are being tested, most so far appear to extend life by a matter of weeks.
"We're not talking about anything that adds years of life to a patient's prognosis. We're talking weeks or months at the most," Sontheimer said.
Patients who have seizures because of the tumors, as Kennedy did last weekend, usually also take anti-seizure medication, Laureno said. The seizures are typically caused by tumors located near the surface of the brain, where they disrupt the normal electrical activity.
"Nerve cell networks can get irritated by the tumor. The brain sort of fires off, almost like an electrical storm, and that can make you lose consciousness and have a convulsion," Laureno said.
Over time, the growth of the tumor can cause a range of complications as it damages more parts of the brain.
Despite the bleak outlook, several experts said it is impossible to predict what will happen for any individual patient.
"We do have some long-term survivors who are doing very well," Taylor said. "I think it would be unfortunate to say it's grim. It could go that way. But I don't think it's destined to go that way."