Cancer is not a random bunch of selfish rogue cells behaving badly, but a highly-efficient pre-programmed response to stress, honed by a long period of evolution.In short, if you stress the human organism sufficiently, you will awaken primal genetic programming that causes cancer to develop in individual cells as a survival adaptation. This programming developed about a billion years ago, at a time when the earth was experiencing much harsher environmental conditions than we have today, so these cells can survive in low-oxygen environments and ultimately thumb their noses at anything medicine can throw at them in the way of chemotherapy or radiation.
This new hypothesis completely reverses the current view of cancer. Rather than being an unhealthy occurrence within a healthy body, it is an archaic survival response to conditions that threaten the body, i.e., an effort to reestablish health. The author of the article concludes
we need to shift our thinking away from the view that cancer is something unnatural that happens to us, to one where we see that cancer is something natural our body does to survive unnatural conditions. Change and improve those conditions, and you do more to change cancer than [by] attacking it as if you were fighting a war against an enemy.As my summary is quite sketchy, I heartily recommend reading the article in full.