After being diagnosed with metastatic cancer, former President Jimmy Carter's doctors said he no longer needs cancer treatment. President Carter's remarkable turnaround is credited in large part to the drug pembrolizumab, which targets cancer by ramping up the body's immune system.

Dr. Jedd D. Wolchok, oncologist and researcher at Sloan Kettering, talked about how doctors are treating people with melanoma and working to develop innovative ways to use the immune system to treat cancer.

To date, the diseases that respond best are those that have a lot of genetic damage. Cancers like melanoma, kidney cancer, bladder cancer, and some kinds lymphoma, which are caused by sun exposure and tobacco use.