Jimmy CarterWhen former President Jimmy Carter announced recently that his cancer was in full remission, he also disclosed that he had been receiving a groundbreaking new treatment called immunotherapy. When he was diagnosed in August 2015, Carter had surgery, following by radiation. Then he began the drug pembrolizumab, which accelerates the body’s own immune response. According to ABC News:

The drug works as a “checkpoint inhibitor,” altering certain pathways in the immune system so that the antibodies can identify and fight any tumors in the body the way they might fight a virus or cold, experts said. The medication is much less toxic than chemotherapy, but it can react in colon, liver or lung inflammation, according to published studies. Researchers are still trying to determine how long the medication can prompt the immune system to keep fighting.

Immunotherapy is not a single drug. It is actually a broad range of therapies that utilize the body’s own immune system to fight malignant cells. When you have cancer, these cells divide rapidly, like an out-of-control copy machine. The abnormal cells are constantly mutating to outwit the immune system. Immunotherapy finds and destroys these cancer cells.

Your immune system is constantly patrolling every system of your body, on the lookout for foreign invaders such as bacteria, fungi and viruses. Your white blood cells, such as T cells, fight off these invaders. The immune system does not recognize cancer cells as a danger, because they are your body’s own cells. This allows malignant cells to continue to grow, divide, spread and adapt throughout your body. One method malignant cells use to stay hidden is through the PD-1 receptor, which tricks the immune system. Immunotherapy drugs suppress the PD-1 inhibitor, allowing the cancer cells to be identified as a danger and alerting the immune system to attack them.

Immunotherapy drugs work better against some cancers than others. They may be an option for breast, prostate, brain (as in President Carter’s case), kidney and spinal cancer, as well as non-Hodgkin lymphoma, leukemia or melanoma. Immunotherapy is often prescribed in concert with other treatments.

This treatment is not without side effects. Some people experience fatigue, nausea, sores in the mouth, diarrhea, high blood pressure and buildup of fluid, particularly in the legs. Breast cancer patients have been known to have fevers, chills, pain, weakness, vomiting, headaches and rashes, but the side effects are usually much less severe after the initial treatment.

No one knows at this point how long immunotherapy drugs will work, and whether they provide a permanent cure. Still, this is one of the most promising developments available in our fight against cancer.