The 39th president had learned in May that he had a "small mass" on his liver and decided to have the elective surgery to remove it on August 3. At that time the Carter Center, his nonprofit organization, released a statement saying "the prognosis is excellent for a full recovery."
But by August 19, a Carter Center statement told a different story. Tests after the liver surgery revealed the cancer was melanoma. An MRI revealed there were four spots of melanoma on his brain. Doctors said the small spots were about 2 millimeters in size.
Stage IV melanoma
is a kind of cancer that starts in the cells that produce the pigment that gives your skin its color, known as melanocytes. Stage IV means it spread via the bloodstream or through the lymphatic system to other areas of the body.
Skin cancer is the most common kind of cancer in the United States, according to the Centers for Disease Control and Prevention
. And melanoma
is the deadliest form of it. According to the National Cancer Institute, an estimated 76,100 Americans will be diagnosed with melanoma and 9,710 will die from the disease this year. The exact cause of his cancer isn't clear, though; Carter said doctors will continue to search for the source. Some 98% of melanomas do start with the skin, and lessening your exposure to ultraviolet light
does lower your risk of skin cancer.
The 90-year-old had a significant book tour planned this year to promote his latest memoir, "A Full Life: Reflections at Ninety," but decided to rearrange his schedule to fit in the treatment.
At no point did he consider going without treatment, he told CNN Chief Medical Correspondent Dr. Sanjay Gupta. The former president said he would trust the advice of his doctors.
Focused radiation treatment
Thursday afternoon, Carter was to undergo radiation treatment.
On Wednesday, the hospital fitted him with a mask that will hold his head perfectly still to make sure the radiation goes into the right places in his brain. "Focused radiation as compared to general radiation has shown some success," said Dr. Manmeet Ahluwalia
. "That they are really small makes it more likely that these lesions can be controlled."
Ahluwalia is Cleveland Clinics director of the Brain Metastasis Research Program and the associate director for clinical trials, and he has tested this kind of treatment.
Doctors also will give Carter the drug Pembrolizumab
-- known by its U.S. brand name Keytruda -- intravenously. The Food and Drug Administration approved the drug in September 2014
to treat melanoma that cannot be removed by surgery, or a cancer that has metastasized. He has four treatments scheduled at three-week intervals.
"Most of the time we would use radiation on this kind of cancer but more recently, in the last couple of years, we were finding out drugs can impact brain metastases," Ahluwalia said. A presentation of a study at the American Society of Clinical Oncology this May showed that the drug has had some successes with patients.
Essentially, the drug works by revving up a patient's own immune system to kill the cancer, according to Ahluwalia.
This aggressive mix of treatments, treatments Carter's oncologist characterized as "the vanguard of cancer treatment," may have a positive impact, but positive impact does have its limitations. Typically with Stage IV melanoma there are "not very good outcomes," Ahluwalia said. Often people will be given a ballpark of six to 12 months to live if they have brain metastases. "However, what we are finding out (is) a select group of patients can derive more durable benefit from Pembrolizumab" and radiation. "But the emphasis is on the word 'select' and even that group typically lives only two to three years longer, but it is still a minority of patients and we also need to factor in the age, which can be important."
'He has a lot to live for'
What is working in Carter's favor, Ahluwalia said, is the active life that Carter leads. Sometimes, he said, that is nearly as big a factor in outcome as age. People who have the sort of positive attitude Carter displayed at the press conference "generally do better."
Carter has watched many of his family members struggle with cancer. He lost his father and all his siblings to pancreatic cancer. His mother died after having breast cancer.
What impact this treatment will have on his life going forward is up for debate. Carter said he had hoped to join a Habitat for Humanity
build scheduled later this year to replace homes lost in the earthquakes in Nepal, but said he understands that he will generally have to cut back on his busy schedule.
In an interview with CNN's Gupta, Carter's doctor Dr. Walter Curren said that the new therapies made available in the past five years have "far less side effects than standard chemotherapy." He added, "You heard President Carter. He wants to be proactive, he has a lot to live for, and what we offered him is a regimen a man in good health his age can handle."