Sen. John McCain says that he has received a "very poor" prognosis from doctors regarding his brain cancer.

McCain, 81, revealed the severity of his diagnosis during an interview with CBS's "60 Minutes."

"They said that it's very serious," McCain said. "That the prognosis is very, very serious. Some say 3 percent, some say 14 percent. You know, it's a very poor prognosis."

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The Arizona Republican announced that he had been diagnosed with brain cancer in July after he had surgery for a tumor, according to The Associated Press. The tumor was found to be glioblastoma, the same type of cancer McCain's former colleague, Ted Kennedy, had.

"I think about Ted a lot," McCain told "60 Minutes." "Ted stayed at his job, kept working. Kept going even when he was in a wheelchair. And he never gave up because he loved the engagement."

McCain told the show he starts his day with chemo and radiation before going in for a full day of work in the Senate.

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"I am more energetic and more engaged as a result of this because I know that I've got to do everything I can to serve this country while I can," he said.

Despite his diagnosis, McCain has remained a major figure in the Senate, twice dashing Republican efforts to repeal Obamacare.

Eleven days after his surgery in July, McCain returned to Washington to cast the decisive vote against an Obamacare repeal. In September, McCain opposed anther repeal effort despite it being co-sponsored by his close friend, Sen. Lindsey Graham.

Those decisions put McCain at odds with President Donald Trump. The two have had a strained relationship since then-candidate Trump claimed McCain wasn't a war hero.

"He was a war hero because he was captured. I like people who weren't captured," Trump said in 2015, according to Politico.

McCain, a Navy pilot during the Vietnam War, spent more than five years in a North Vietnamese prison, where he was tortured and placed in solitary confinement.

McCain told "60 Minutes" he doesn't dwell on negative things that others say about him and he would be open to a better personal relationship with Trump.

"I'd be glad to converse with him," McCain said. "But I also understand that we're very different people. Different upbringing. Different life experiences. ... He is in the business of making money and he has been successful both in television as well as Miss America and others. I was raised in a military family. I was raised in the concept and belief that duty, honor, country is the lodestar for the behavior that we have to exhibit every single day."

Sources: AP via Star Tribune, 60 Minutes / Featured Image: Gage Skidmore/Flickr / Embedded Images: Max Pixel (2)