Sen. Edward Kennedy is midway through a six-week course of radiation and chemotherapy treatments for brain cancer, and other than some fatigue, his wife says he's doing well.

In an e-mail update to family and friends sent Wednesday, Vicki Kennedy says her husband has been exercising each morning before heading to Boston for treatment at Massachusetts General Hospital. By afternoon, he's back at his family compound in Hyannis Port and sailing on his schooner "Mya."

"The only side effect is fatigue, and that word has never been in Teddy's vocabulary before," Vicki Kennedy wrote in an e-mail The Associated Press obtained Monday. "But he's learning to cope with it. As I have mentioned to many of you, he is tackling cancer with his trademark grit and determination, and he is doing everything he needs to do to regain his strength and health."

Kennedy had a seizure at his Cape Cod home on May 17 and was subsequently diagnosed with a malignant brain tumor. The Massachusetts Democrat underwent surgery at Duke University Medical Center on June 2 and has been treated since in Boston.

"He exercises every morning before we make our trek to Boston, and sails almost every afternoon when we get back to the Cape. I have drawn the line at sailing in thunderstorms, but other than that, he's out on the water just about every day. He's making calls, staying in touch with his office staff and colleagues and still pushing all the issues he cares about," Vicki Kennedy wrote.

One aim is a rejuvenated push for a federal universal health care bill whenever Kennedy is able to return to the Senate. The senator has made health care and pension issues a trademark since first being elected in 1962.

Despite the upbeat assessment, Kennedy's treatments did interfere with one tradition: Last week, the couple could not make their annual sail to Sag Harbor to mark their wedding anniversary. They were married 16 years on Thursday.

Instead, the Kennedys made a day trip on Nantucket Sound.

Vicki Kennedy closed her note by saying her husband describes his cancer as "a bear," but she thinks of his reputation as a political fighter and an old-school liberal.

"My guy's a lion," she wrote. "I'm betting on the lion."