The investigators doing this study are interested to find out whether patients with melanoma live as long when the PD-1 inhibitors are given continuously (non-stop) or in an intermittent schedule (taking breaks). If the two ways of giving the treatment were to be shown to be just as good, benefits of an intermittent schedule may include less clinic visits and side effects, better quality of life, and less cost over time for the Health Care System. However, this is not known at present.