Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) on Sunday said he is facing a "very vicious" form of cancer, but he expressed confidence in his prognosis.

"The prognosis is pretty good ... This is a very vicious form of cancer that I'm facing," McCain said on CNN's "State of the Union."

"All the results so far are excellent. Everything is fine. I have just more energy than ever ... I'm just fine."

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McCain, who underwent his first round of chemotherapy to treat brain cancer, said he's facing a challenge.

"But I've faced other challenges and I'm very confident about getting through this one as well," he said.

He said he's very happy with what he's been able to do and is able to "celebrate a wonderful life."

"I will be grateful for additional time that I have," McCain said.

He also thanked those who have been treating him for their care.

"Every life has to end one way or another," he said. "You got to have joy."

At the end of the interview, McCain said he hoped people would remember him as someone who served his country.

"Made a lot of mistakes, made a lot of errors, but served his country, and I hope we could add honorably," he said.

McCain was diagnosed earlier this year with a glioblastoma, one of the most aggressive types of brain tumors.

He returned to the Senate last week, after undergoing his first round of chemotherapy and radiation treatments.