WASHINGTON (AP) — 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. Survival statistics are grim — few live three years and for the worst subtype, half die within a year.

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

Kennedy's doctors didn't mention surgery, suggesting that may not be a possibility for him.

"As a general rule, at 76, without the ability to do a surgical resection, as kind of a ballpark figure you're probably looking at a survival of less than a year," said Dr. Keith Black, chairman of neurosurgery at Cedars-Sinai Medical Center.

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 newly diagnosed 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. Tuesday, doctors at Massachusetts General Hospital announced the reason, a malignant glioma in his left parietal lobe, a brain region that governs sensation but also plays some role in movement and language. Doctors were awaiting further tests before choosing treatment, but they cited radiation and chemotherapy as the usual 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, known for claiming entertainer Ethel Merman and Republican political strategist Lee Atwater — or the only somewhat less aggressive anaplastic astrocytoma, Subramaniam said.

Malignant glioma "usually is a synonym for a glioblastoma," agreed Dr. Robert Laureno, neurology chairman at Washington Hospital Center in the nation's capital.

The American Cancer Society puts the five-year survival rate for patients over age 45 at 16 percent for those with anaplastic astrocytomas, and 2 percent or less for those with glioblastomas.

Patients fare best when surgeons can cut out all the visible tumor, Black said. That isn't a cure — doctors know they're leaving cancerous cells they just can't see.

But about 40 percent of the time, surgery isn't an option. The cancer, which digs tentacle-like roots into normal brain tissue, may be too deep or located so closely to critical brain regions.

Moreover, "it doesn't help to take 50 percent or 60 percent of the tumor out," Black said.

Standard treatment is about six weeks of fairly high-dose radiation along with a chemotherapy pill named Temodar, and then additional Temodar for at least six months or until the tumor stops responding.

The older the patient, the worse the prognosis. But some people fare much better — especially those with a subtype where another glioma form, called oligodendroglioma, is mixed with the primary tumor, Black said. They generally survive three times as long as people with pure glioblastomas.

The tumor's size — which also wasn't revealed — is key, too, added Dr. Lynne Taylor of Seattle's Virginia Mason Cancer Center and the American Academy of Neurology. An 8-centimeter tumor is pretty big for chemo and radiation to blunt, while a 1cm tumor is easier.

Also, the fairly recent addition of Temodar has brought a slight increase in the number of patients who beat average survival odds, she added.

"You're fighting an uphill battle," is what Taylor tells her patients — and then immediately urges them to live as if they'll be one of the lucky ones.

Whatever the statistics, the news is grim. And what symptoms will appear first depends on exactly where in the parietal lobe the tumor sits and "how that individual's brain is wired," Laureno said.

Among the possibilities: Loss of sensation on the right side of the body, problems with movement in the right arm and leg, eventual problems speaking or even vision problems in the right eye.

There are some experimental therapies that researchers are watching closely, including:

—Adding the colon cancer drug Avastin to standard treatment. Avastin chokes off tumors' blood supply, and initial studies suggest it can help shrink gliomas. Whether that helps survival isn't yet known, but Black says even though this use is experimental, more and more specialists are prescribing it right after diagnosis.

—Trying experimental cancer vaccines. Brain tumors often can't be seen by the immune system. So scientists take cells from the surgically removed glioma, put them on the immune cells and give them back to the patient. Small studies at Cedars-Sinai suggest the approach improved two-year survival from 8 percent of glioblastoma patients to 42 percent, Black said. But it's only an option for surgery candidates.

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BOSTON (AP) — Sen. Edward M. Kennedy was diagnosed with a cancerous brain tumor Tuesday in what could be the grim final chapter in a life marked by exhilarating triumph and shattering tragedy. Some experts gave the liberal lion less than a year to live.

Doctors discovered the tumor after the 76-year-old senator and sole surviving son of America's most storied political family suffered a seizure over the weekend. The diagnosis cast a pall over Capitol Hill, where the Massachusetts Democrat has served since 1962, and came as a shock to a family all too accustomed to sudden, calamitous news.

"Ted Kennedy and the Kennedy family have faced adversity more times in more instances with more courage and more determination and more grace than most families have to," said Sen. John Kerry, D-Mass. "Every one of us knows what a big heart this fellow has. He's helped millions and millions of people — from the biggest of legislation on the floor to the most personal."

Kerry added: "This guy is one unbelievable fighter."

Kennedy's doctors at Massachusetts General Hospital said he had a malignant glioma in the left parietal lobe, a region of the brain that helps govern sensation, movement and language.

Seizures can be caused by a wide variety of things, some of them relatively minor. The finding of a brain tumor — and specifically a glioma, an especially lethal type — was about the worst possible news.

Kennedy's doctors said he will remain in the hospital for the next couple of days as they consider chemotherapy and radiation. They did not mention surgery, a possible indication the tumor is inoperable.

Outside experts gave him no more than three years — and perhaps far less.

"As a general rule, at 76, without the ability to do a surgical resection, as kind of a ballpark figure you're probably looking at a survival of less than a year," said Dr. Keith Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles.

In a statement, Dr. Lee Schwamm, vice chairman of neurology at Massachusetts General, and Dr. Larry Ronan, Kennedy's primary physician, said the senator "has had no further seizures, remains in good overall condition, and is up and walking around the hospital."

"He remains in good spirits and full of energy," the physicians said.

An Associated Press photographer who was given access to the senator on Tuesday captured Kennedy, dressed in a gray sweater and dark slacks, joking and laughing with family members as he sat at a table in a family room at the hospital.

Kennedy's wife since 1992, Vicki, and his five children and stepchildren have been at his bedside.

"Obviously it's tough news for any son to hear," said Robin Costello, a spokeswoman for one of Kennedy's sons, Rep. Patrick Kennedy, D-R.I. "He's comforted by the fact that his dad is such a fighter, and if anyone can get through something as challenging as this, it would be his father."

Kennedy, the Senate's second-longest serving member, was re-elected in 2006 and is not up for election again until 2012. Were he to resign or die in office, state law requires a special election for the seat 145 to 160 days afterward.

Among the potential Democratic candidates: Martha Coakley, the state's attorney general; Rep. Edward J. Markey; former Rep. Joseph P. Kennedy II, Kennedy's nephew; and Kennedy's wife. The Republican contenders could include former Gov. Mitt Romney or former Lt. Gov. Kerry Healey.

Kennedy has left his stamp on a raft of health care, pension and immigration legislation during four decades in the Senate.

Senators of both parties heard about Kennedy's condition during their weekly, closed-door policy lunches, and some looked drawn or misty-eyed.

Sen. Robert Byrd, D-W.Va., the longest-serving member of the Senate, wept as he prayed for "my dear, dear friend, dear friend, Ted Kennedy" during a speech on the Senate floor.

"Keep Ted here for us and for America," said the 90-year-old Byrd, who is in a wheelchair. He added: "Ted, Ted, Ted. My dear friend. I love you and miss you."

"I'm really sad. He's the one politician who brings tears to my eyes when he speaks," said former Sen. Bob Kerrey, D-Neb., who happened to be in the Capitol.

In a statement, President Bush saluted Kennedy as "a man of tremendous courage, remarkable strength and powerful spirit." He added: "We join our fellow Americans in praying for his full recovery."

Malignant gliomas are diagnosed in about 9,000 Americans a year. In general, half of all patients die within a year.

"It's treatable but not curable. You can put it into remission for a while but it's not a curable tumor," said Dr. Suriya Jeyapalan, a neuroncologist at Beth Israel Deaconess Medical Center in Boston.

The Kennedy family has been struck by tragedy over and over. Kennedy's eldest brother, Joseph, died in a World War II plane crash; President John F. Kennedy was assassinated in 1963; and Sen. Robert F. Kennedy was assassinated in 1968. The tragedies thrust "Uncle Teddy" into the role of surrogate parent to his brothers' children. He walked Caroline Kennedy down the aisle.

A high point in his life came in 1980, when Kennedy challenged Jimmy Carter for the Democratic presidential nomination. He eventually bowed out with a stirring speech in which he declared, "The cause endures, the hope still lives and the dream shall never die." His eulogy for his brother Robert was equally stirring.

The low point was 1969, when Kennedy drove a car off a bridge on Chappaquiddick Island on Martha's Vineyard. The accident killed aide Mary Jo Kopechne. Kennedy at the time was married to his first wife, Joan, whom he later divorced. His failure to promptly report the accident, and questions about his relationship with the young woman, may well have cost him the presidency.

Kennedy has been active for his age, maintaining an aggressive schedule on Capitol Hill and across Massachusetts. He has made several campaign appearances for Sen. Barack Obama.

"He fights for what he thinks is right. And we want to make sure that he's fighting this illness," Obama said Tuesday. "And it's our job now to support him in the way that he has supported us for so many years."

Sen. Hillary Rodham Clinton said: "Ted Kennedy's courage and resolve are unmatched, and they have made him one of the greatest legislators in Senate history. Our thoughts are with him and Vicki and we are praying for a quick and full recovery."

Last summer, Kennedy announced a deal with a publisher to write a memoir, scheduled to come out in 2010.

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Associated Press Writer Lauran Neergaard contributed to this report from Washington.