Once melanoma takes hold as in the dads situation it seems to explode. This was the case with my sisters fiance and another melanoma patient I knew. At this stage I would go along with the trial protocol as this is his best chance for any extension of life. Some patients respond remarkably well in trials, unfortunately, most patients are at their last resort before able to partake. I would disagree with the doctor who says you dads health is not in danger. It may be true that otherwise he is healthy but cancer has no mercy and can turn otherwise healthy tissue into tumor quickly. Do whatever to give you dad some quality time and say whatever needs to be said.