"The cancer drug that former president Jimmy Carter says made his melanoma seemingly disappear has helped about  percent of similar patients survive for as long as three years oncologists said Wednesday. The drug called Keytruda takes a new approach to treating cancer by stopping tumor cells from cloaking themselves against the normal healthy immune system response. New data about to be released to a meeting of cancer specialists shows that  percent of the patients who have been taking the drug are still alive three years later. That compares to about  percent of patients given the standard therapy interleukin the American Society for Clinical Oncology ASCO says. That means  percent of patients are not living that long  but its still far more than the usual month survival with advanced melanoma. It is definitely a huge benefit over what we have seen in the past said ASCO president Dr. Julie Vose a specialist in blood cancers at the University of Nebraska Medical Center. For some of those patients it is likely that their cancer never will come back. Melanoma is the deadliest form of skin cancer. It will be diagnosed in more than  Americans this year according to the American Cancer Society and it will kill . Rates are rising in part because tanning became fashionable. Melanoma is easy to cure when caught early but it is often hard to tell if a mole or freckle has turned cancerous. Carter for example was only diagnosed  http the tumors had spread to his brain last fall. Thats Stage IV cancer and its almost always deadly at that stage. But Carter has remained well enough to continue teaching his weekly Sunday school classes and said this past Sunday hed just traveled to London. He says theres no trace of his cancer now. In the past patients with this type of melanoma  he has metastases to the brain  you dont even see responses to therapy Vose told NBC News. This is something really different than what we have seen in the past. Other people are having similar experiences. For the trial Caroline Robert of Gustave Roussy and ParisSud University in France and colleagues treated  patients with advanced melanoma. These are patients whose disease cannot be surgically removed cannot be cured by surgery and usually the majority of these patients have disease that involved vital organs said Dr. Stephen Hodi a melanoma specialist at the DanaFarber Cancer Institute who worked on the study. Seventyfive percent of them had already been given other cancer treatments including Yervoy known generically as ipilimumab. On average the patients lived two years and  percent of them are still alive three years later. About  percent of these patients have whats called a complete remission meaning there is no trace of their tumors. That doesnt mean a cure  its too soon to say that  but it does mean months or years of cancerfree life that they otherwise could not have hoped for. And  of the patients or  percent have stopped taking the drug after their tumors went away. Virtually all of them are still in remission.  This is huge in the melanoma community said Tim Turnham executive director of the Melanoma Research Foundation. Its difficult to know at what point you call it a cure. For the patient though it means they are cancerfree and for some of those patients it is likely that their cancer never will come back Turnham told NBC News. When this study was started the average life expectancy of someone with advanced melanoma was  months and now were seeing that a large percentage of people are living at least three years. Keytruda  known generically as pembrolizumab http  targets the activity of genes called PD antiprogrammeddeathreceptor and PDL. The interaction between the two genes lets some tumors escape detection and destruction by immune system cells. PD stops immune cells from attacking normal healthy cells by mistake. Tumor cells make PDL turn on PD when immune cells approach. Keytruda an engineered immune protein called a monoclonal antibody disrupts this signal and lets the immune cells attack the tumor cell. The drug works far better in patients whose tumors express more PD meaning they have a lot of PD activity so the drug will optimally be used jointly with a test for PD. There are sideeffects including fatigue itchiness and rash. It was bad enough for  percent of patients that they stopped taking it. In a matter of a few years these therapies have truly transformed the outlook for patients with melanoma and many other hardtotreat cancers. The Food and Drug Administration gave Keytruda accelerated approval for melanoma i http . Its got breakthrough therapy designation for Hodgkins lymphoma and colon cancer and got accelerated approval for lung cancer. In a matter of a few years these therapies have truly transformed the outlook for patients with melanoma and many other hardtotreat cancers said Dr. Don Dizon an oncologist at Massachusetts General Hospital and a spokesman for ASCO. Keytrudas being tested in other cancer types now. Earlier Wednesday the FDA gave accelerated approval to a drug that works in a similar way. It approved Tecentriq known generically as atezolizumab for use in patients with advanced bladder cancer. Like Keytruda Tecentriq is a monoclonal antibody. It goes straight to PDL so its target is slightly different. FDAs approval was made on the basis of a trial that showed  percent of patients with advanced bladder cancer who had high levels of PDL activity saw their tumors disappear compared to . percent of patients on other treatments. Another  percent had a partial response meaning their tumors shrank a little compared to . percent on standard treatment. The drugs must be infused and they are pricey. Keytruda costs about  a month or  a year."