Former President Jimmy Carter said he and his wife, Rosalynn, are going to "cut back dramatically" on their public schedule as he begins radiation therapy later today.

During a press conference in Atlanta, Carter said doctors found melanoma that had spread to his liver and his brain. Ninety-eight percent of that kind of cancer first shows up on the skin, he said. Two percent develops first inside the body.

Carter, who is 90, said doctors initially detected a small mass in his liver. When they scanned his neck and brain after surgery to remove the mass, they found four other spots in his brain.

"I just thought I had a few weeks left," he said. "But I was surprisingly at ease. I've had a wonderful life ... I've got thousands of friends."

"Surprisingly at ease," he repeated. "Much more than my wife."

Carter said that his future is now in the "hands of God and my worship. And I'll be prepared for it if it comes."

The former president did not specifically say if doctors told him how long they believed he had to live.

Carter is the son of a peanut farmer. He served as the country's 39th president from 1977 to 1981. After his time in office, he founded the Carter Center, advocating for peace, democracy and human rights.

During the press conference, Carter was asked about the future of the center (it's "well prepared to continue without any handicap"), the best thing he ever did ("marry Rosalynn") and about his biggest regret.

"I wish I had sent more helicopters to rescue the hostages," he said, referring to a failed military operation in 1980 to free 52 American hostages being held in Iran.

Had he done that, Carter said, he would've won a second term and he would've still founded the Carter Center.

"I could've done both," he said.

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