As for Ken's above point # 2, I think some clarification is in order because its' incorrect. Cancer is easily misunderstood.
Cancer can extract oxygen and nutrients from blood, preferentially most of the time. It often outgrows its' budding blood supply and become necrotic because it tends to grow quicker than other cells. Also the reason for weight loss while afflicted, the cancer is preferentially taking nutrients such as glutamine.
The mainstay of most chemotherapy (caveat: The newer monoclonal antibodies etc I am only slightly familiar with) is to target fast-replicating cells, i.e. cancer, which is why other cell lines than turn over quickly (hair, nails, GI lining) feel the brunt as well.
I think the problem most people have with grasping cancer is a fundamental misunderstanding of the disease process. Cancer is your own cells, which through a process too long to discuss here, lose their ability to undergo programmed death when damaged, and essentially proliferate without end, spreading to different parts of the body either locally, through blood, or through lymphatics. When tumor suppressor genes on chromosomes fall off or are damaged/mutated, you can't just pop it back on, though people are researching novel genetic treatments all the time, and I hope they eventually will be successful.
We do, actually, have a cure for cancer if caught early enough. Frank can tell you what it is
Just trying to clarify a little,
Tony