ATLANTA - Former President Jimmy Carter said Sunday that his latest brain scan "did not reveal any signs of the original cancer spots nor any new ones," more than three months after he began treatment for four melanoma tumors.

His brief statement followed reports that he had shared the good news with a Sunday school class at Maranatha Baptist Church in his hometown of Plains, Ga.

"I went to the doctors this week for the second time," Carter, 91, said in a video posted on Twitter by NBC News. "The first time I went for an MRI of my brain, the four places were still there but they were responding to the treatment. And when I went this week, they didn't find any cancer at all. So I have good news."

Carter smiled slightly as people in the congregation responded with applause.

"So a lot of people prayed for me, and I appreciate that," Carter said.

Carter's statement said he will continue to receive regular doses of Keytruda, a recently approved auto-immune drug, to help his body seek out any cancer cells appearing in his body.

Carter announced in August that he had been diagnosed with melanoma that spread to his brain. Doctors removed a portion of his liver and found four small tumors on his brain. He received a round of radiation targeted at those tumors and doses of Keytruda every three weeks.

Carter's grandson Jason Carter told the Associated Press earlier Sunday in a text message that his grandfather on Friday "told me that the doctors couldn't find any cancer in his most recent scan."

Jill Stuckey, a Maranatha Baptist member, said Carter arrived with his wife, Rosalynn, greeted the roughly 300 people at his Sunday school class, then shared the scan results.

"There were a lot of happy people at the church. I went running down the hall and got to spread the news," she said. "Our prayers have been answered."

It's not clear what other scans Carter's medical team at Emory University's Winship Cancer Institute have performed. A spokesman didn't immediately return messages on Sunday and Carter only mentioned a brain scan.

Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, said doctors evaluating melanoma patients will use scans of other body parts beyond where the disease has been found to ensure it has not spread. "For today, the news cannot be better," Lichtenfeld said. "Circumstances may change over time or he may be in a situation where it does not recur for many years or at all."

He said he expects Carter's doctors will continue "close surveillance" for any new cancer growth or recurrence in his brain and continue doses of the immunotherapy drug as long as Carter handles it well.

More than perhaps any other cancer, melanoma has been transformed by the advent of immunotherapy treatments. The FDA has approved seven new drugs for the disease since 2011, four of them immune therapies and three "targeted" drugs for particular types of melanoma.

This article contains information from the Washington Post.