BOSTON (AP) -- Sen. Edward Kennedy, who has brain cancer, has returned home after being taken to a hospital by ambulance because he had suffered a seizure, his staff says.

A statement issued by his office attributed the "minor seizure" Friday to a change in medications. He was back home a few hours later.

Sen. John Kerry said his fellow Massachusetts Democrat was well and had told him he would watch the evening's presidential debate between John McCain and Barack Obama.

Kennedy, 76, had another seizure in May and underwent surgery in June for a malignant brain tumor.

He has been steadily increasing his public activity since undergoing six weeks of chemotherapy and radiation treatment, but he remains prone to seizures -- electrical disturbances in the brain -- in part because of the location of his tumor, the left parietal lobe. Among other functions, it controls speech.

A 911 call was placed from the Kennedy compound in Hyannis Port just after 5 p.m. Friday, said Barnstable police Sgt. Ben Baxter. Kennedy was taken to Cape Cod Hospital and was "alert and responsive" during the trip, Baxter said.

Kennedy's office said he returned home about 8 p.m.

Kennedy had told reporters in Hyannis Port on Tuesday that he was actively following the presidential race. "I'm going to be following it particularly next Friday," he said with a laugh.

In his opening statement, McCain noted his colleague's hospitalization, saying: "Our thoughts and prayers go out to the lion of the Senate." The Republican nominee worked with Kennedy recently on immigration legislation, although Kennedy has endorsed Obama for president.

Kennedy was visited at his home Tuesday by Chilean President Michelle Bachelet. It was his first public appearance since his surprise speech in August at the Democratic National Convention.

At Tuesday's meeting, the senator stumbled momentarily when he tried to walk on the thick grass, but he quickly regained his balance. He didn't take questions from reporters.

In early September, Kennedy announced he would not return to the Senate until January, although he has since held videoconferences with his staff and members of the Senate Committee on Health, Education, Labor and Pensions, which he leads.

(Copyright 2008 by The Associated Press. All Rights Reserved.)