Jimmy Carter's remission shows power of new cancer drugs

Former president Jimmy Carter's successful treatment for melanoma shows the progress scientists have made in treating cancer, experts told USA TODAY.

Carter, 91, announced his cancer was in remission at the Sunday school class he regularly teaches at a church in Plains, Ga. According to the Carter Center, his most recent brain scan "did not reveal any signs of the original cancer spots nor any new ones."  He has not said that he is cured, and experts say his cancer could still come back.

Carter has had surgery to remove tumors from his liver and radiation to treat the cancer's spread to his brain. In addition, the former president said he'll continue to receive treatments every three weeks with a drug called pembrolizumab, also known as Keytruda.

The drug is part of a new class of drugs that fight cancer by boosting the body's immune system. Keytruda, which costs $150,000 a year, is one of eight new melanoma drugs approved since 2011, said Timothy Turnham, executive director of the Melanoma Research Foundation. Although none of the new drugs has been proven to cure cancer, their arrival was welcome news to patients and cancer advocates. The FDA didn't approve any new melanoma drugs at all from 1998 to 2011.

About one-third of patients who take Keytruda get a benefit, either because the cancer shrinks or stops growing, said Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. Like other doctors interviewed for this story, Lichtenfeld has no personal knowledge of Carter's case. It's not possible to know whether radiation or Keytruda should get credit for the remission, he said.

"People who respond to drugs like Keytruda tend to respond for a while," Turnham said. "There is every likelihood that when he dies, it will be from something other than melanoma."

Immune therapies are approved for lung and kidney tumors as well as melanoma, said Dale Shepard, medical oncologist at Cleveland Clinic.They're being studied in other cancers as well.

Immune therapies work differently than older drugs.

The first cancer drugs, developed in the 1940s, were chemotherapies, which kill growing cells, Shepard said. While these therapies can kill cancers — which grow rapidly — they also kill normal growing cells, such as the cells lining the gut or blood cells. That's why people treated with chemotherapy often develop anemia, nausea and vomiting, and can be vulnerable to life-threatening infections.

In 1998, the Food and Drug Administration approved the drug Herceptin for breast cancer. It was part of a new breed of "targeted therapies," designed to kill cancer cells, rather than all growing cells. That was followed in 2001 by the approval of Gleevec — one of the few real wonder drugs in cancer — for chronic myeloid leukemia. Scientists were able to design these cancer-specific drugs because of a greater understanding of the genes that drive cancer.

But targeted therapies have their own limitations, Shepard said. Although targeted therapies can block parts of cancer cells that promote growth, tumor cells often adapt, finding a "workaround" that allows them to begin growing again.

The new immune therapies don't kill cancer cells directly. Instead, they aim to rev up the immune system, Shepard said. Although the immune system can reliably recognize and kill invaders like bacteria and viruses, the immune system often looks the other way on cancer cells, which don't appear foreign. That's because cancers don't come from outside the body; they are malignant versions of a patient's own cells.

Immune therapies aim to "unmask" cancer cells, so that the body recognizes them as the dangerous killers that they are, Shepard said.

Cases such as Carter's —  in which the cancer spreads to the brain — can be especially difficult to treat, Turnham said. Few drugs can get past the "blood-brain barrier," a system that protects the brain from bacteria and infections. But drugs such as Keytruda appear to help shrink brain tumors indirectly, by revving up immune cells that can cross into the brain, he said.

While all drugs cause side effects, immune therapies are often gentler than traditional chemotherapy. Shepard notes that Carter has only missed two sessions of Sunday school.

While the new cancer therapies may not cure cancers, they can sometimes keep them under control for a long time. Doctors now talk about treating cancer as a chronic disease, similar to diabetes and heart disease, Shepard said.

Cancer research is giving hope to people with other cancers, as well. For example, the FDA approved three new drugs to treat multiple myeloma — a cancer of the bone marrow — in November alone.

Turnham said he's concerned that shrinking budgets at the National Institutes of Health could impair this sort of progress. Many people are concerned about the cost of new cancer therapies, which now routinely debut at more than $100,000 a year.

"These breakthroughs that happen quickly don’t come out of a vacuum," Turnham said. "It's like building a skyscraper. You wait for months and there is nothing but a hole in the ground. Then, you turn around and it's 10 stories high. Basic science is like that foundation (of a skyscraper). Once you understand what is going on in the cancer at a biochemical level or a molecular level, you can accelerate and have tremendous progress."