Cure for cancer

There are huge studies of people who have cancer from specific environmental or generic causes. What is the common thread that unites these people so that they all get cancer?
How about this question: What is the common thread that prevented all the others from getting cancer? Wouldn’t those be worth studying? Maybe the human natural system has already found a cure for it, but we are looking for the cause. I know someone much smarter than me is already doing this somewhere. They’d better be. I don’t think I can find the time to go to medical school just to prove my point.
How would you approach this problem?And then let’s discuss the effectiveness of crowdsourcing medical research. Sound good? Go.