You could also just say that Cancer is a flaw in the genes, much like a mutation, which is why many people can smoke all their lifes without catching a cancer while others can not (smoking is just an example) So even though it would be able to give u infinite "hp" it'll still kill you, because the human body is not capable of changing that much over so little time. (Not the big biologist, I've just been informed since I got lung cancer).