This immunotherapy approach is transforming treatment for several kinds of cancer with drugs that are often less toxic than chemotherapy. “This is incredible,” Dr. Caroline Robert, the study’s lead author, said of the results. Keytruda is also known as pembrolizumab and had spectacular results: in the study, many patients remained cancer-free. Rashes and internal inflammation are the most common side but rare effects and they are reversible if the drug is stopped. The yearly cost is however more than $100,000, a higher price than some conventional cancer drugs. The American Cancer Society estimates that almost 77,000 people will be diagnosed with melanoma this year and that 10,000 will die from the disease.