WASHINGTON — A malignant glioma — the diagnosis doctors gave Sen. Edward M. Kennedy — is the worst kind of brain cancer.

Malignant gliomas strike almost 9,000 Americans a year. Few live three years and for the worst subtype, half die within a year.

Who lasts longer depends on exactly what form of glioma someone has, whether surgeons can cut most of it out, age and some other medical details.

On the plus side, scientists are studying new approaches — adding a drug called Avastin to standard treatment, or even brewing up customized vaccines to help the body fight back.

While they're still experimental, many glioma experts advise patients to seek out specialized cancer centers and ask if they're a good candidate for a research study up front.

"Considering how poorly they do despite standard treatment, it is always best to seek a clinical trial," said Dr. Deepa Subramaniam, director of the brain tumor center at Georgetown University's Lombardi Comprehensive Cancer Center. "They are not likely to do worse."

Kennedy was hospitalized Saturday after a seizure. Doctors were awaiting further tests before choosing treatment, but they cited radiation and chemotherapy as the most common approach.

Kennedy's age and the mention of upfront chemotherapy mean the glioma is almost certainly one of the two worst forms: a glioblastoma — the fastest-killing brain tumor, or the somewhat less aggressive anaplastic astrocytoma, Subramaniam said.

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.