We can pretty safely kill microorganisms that are not very much like us be it ticks, typhoid, or trichomonas by simply targeting things they got that we don't. This isn't going to be true if it is our cells that are dividing too fast. Therefore, we are going to have toxicity from a cure for cancer. On the other hand, the toxicity we see from all those treatments we've gotten sure as heck seem to imply a particular site where they're working that we haven't really gone after. And this implies at least 3-6 new drugs for cancer.. that we already have and just haven't tested.