Ironically cyanide is about as deadly as the drugs they used in chemo. I agree with your snake oil salesman comments but sometimes those sales come from people with mds and phds.
The challenge with cancer is that the cells are just as much part of your body as healthy cells. Most schemes to kill disease rely on differences between the body's cells and the disease causing cells--for example, antibiotics target bacterial systems that are not found in animals.
With cancer, there are very few targets that are found only in the cancer but not healthy cells. Because of that, many treatments are based on the fact that cancer cells grow rapidly, but most healthy cells do not. So they target growing cells, and end up killing all cells that are growing, including skin, intestinal lining, and hair cells.
Cancer presents a real challenge to researchers, many of them who are motivated to conduct cancer research because of the death of a loved one.