Just four months after starting treatment for an aggressive form of brain cancer, former President Jimmy Carter announced on Sunday that he is virtually cancer free.

While speaking at his Georgia church on Sunday, the 91-year-old former president said that his latest brain scan showed no sign of cancer.

"When I went this week, they didn't find any cancer at all, so I have good news," Carter told the crowd at Maranatha Baptist Church in Plains, Georgia, according to NBC News.

The former Democratic president also released a brief statement via the Carter Center, saying his "most recent MRI brain scan did not reveal any signs of the original cancer spots nor any new ones."

Carter first revealed in August that he had been diagnosed with melanoma, one of the deadliest of all cancers. He also shared that the cancer had spread from his liver to his brain, where it was found in four spots. Fortunately, a previous MRI test showed the spots of cancer that had developed on his brain were responding to treatment, he said.

Carter said he would continue to receive regular doses of pembrolizumab, a new treatment that is part of a promising class of drugs that works by boosting the body's immune system to fight cancer.

Experts also say that being optimistic and remaining in good spirits has helped Carter beat cancer.

"Hope is an important aspect of surviving cancer," said Cleveland Clinic melanoma oncologist Dr. Marc Ernstoff, according to CNN. "Whether that's faith, religion, mindfulness, any one of many different ways that one can get into that state of mind, it's important to do so."

Dr. Leonard Lichtenfeld, the deputy chief medical officer for the American Cancer Society, added, "It's so important not to give up. The tendency of older patients with cancer, along with their loved ones, and even the doctors taking care of them, is to just accept fate and move on. They grew up in a time when 'fighting' cancer was painful, debilitating and often not successful."