DURHAM, N.C. - Sen. Edward M. Kennedy yesterday endured an aggressive, risky surgery, lying awake on an operating table as a renowned neurosurgeon cut through his skull to attack the brain tumor that is threatening the politican's life.

But the hard part may not be over: The 76-year-old "liberal lion" of the Senate now must undergo a battery of chemotherapy and radiation.

Though doctors deemed Kennedy's surgery a success, it will take time before his medical team knows what success means. Experts say the surgery was designed to reduce the tumor's size and give future treatments a better chance to work - but most patients with tumors like Kennedy's die, even with treatment.

"The main goal is to remove as much of the tumor as possible to give any other therapy that we do a better chance of working," said Dr. John Sampson, associate deputy director of Duke's brain-tumor center.

The sole surviving son of America's most glamorous and tragic political family was diagnosed last month with a malignant glioma, an often lethal type of brain tumor discovered in about 9,000 Americans a year.

Details about Kennedy's exact type of tumor have not been disclosed, but some cancer specialists said it might be a glioblastoma multiforme - an especially deadly and tough-to-remove type - because other kinds are more common in younger people than they are in those who are Kennedy's age.

Cutting a tumor down to size - or "debulking" it - is extremely delicate because of the risk of harming healthy brain tissue that governs movement and speech. But Dr. Allan Friedman, the top neurosurgeon at Duke and an internationally known tumor surgeon who performed the procedure, said Kennedy should not experience any permanent neurological effects.

Doctors said Kennedy had been awake for much of the surgery, which begins with opening the scalp and removing a piece of the skull to expose the brain. Sometimes, to avoid damaging areas that control speech, surgeons use a probe to stimulate parts of the brain, then hold a conversation with the patient.

"I feel like a million bucks. I think I'll do that again tomorrow," the Massachusetts Democrat was quoted by a family spokeswoman as telling his wife immediately afterward.

In the following days, Kennedy will probably be given drugs to prevent brain swelling and seizures, which are possible complications of the surgery. He also will be closely watched for bleeding and blood clots, because strokes are also a risk, though they are uncommon. He is expected to return to Boston in about a week.

"After a brief recuperation, he will begin targeted radiation at Massachusetts General Hospital and chemotherapy treatment," Friedman said. "I hope that everyone will join us in praying for Senator Kennedy to have an uneventful and robust recovery." *