This question (or specifically the indicated belief that "most cancer diagnoses are death sentences") belies the greater ignorance still prevalent in our society with regard to cancer treatment. In truth, and I say this as someone living with Stage 4 lung cancer, there has never been a better time in history to receive a cancer diagnosis. I do not say this flippantly, nor with disregard for the many people suffering through their treatments and hoping for survival. But the fact is, Western Medicine and the scientific community as a whole has made such amazingly dramatic leaps over the past 10 to 20 years that the whole narrative of what it means to " have cancer" needs to be changed.
Granted, it is no walk in the park. I am recovering from a round of chemotherapy as I write this, so I would like to think that gives me a layer of perspective that is relevant. Since the initial X-ray that led to my diagnosis, I have avidly researched all available perspectives on causes and treatments; I have interviewed "survivors" and oncologists and I have been fed a constant stream of information on "alternative" cures. Everyone has an opinion. Most of them have no basis in fact.
The truth is, and I believe this as a basic component of biological life, that "cancer" will never be "cured" per se, because cancer is a natural part of the aging process. Cancer isn't a disease that you can catch; it isn't a virus, it isn't bacterial in origin. Cancer is simply another way of describing cellular mutation that continues to divide and grow and, left to its own devices, may (or may not) take over the "healthy" or normal cells of an organism and eventually cause death for a wide variety of reasons. But taken as individual cases, of the 200+ types of identified cancers, more and more of them are readily treatable to the point where the cancer cells can be significantly killed off and life can continue more or less as normal.
There are a lot of roadblocks to successful treatment, but almost none of them are the fault of Western Medicine. Rather, they lie in a combination of late or poor diagnosis (more an issue with our outdated insurance system than the medical community itself) and a perception that traditional Western treatments do more harm than good -- but mostly in the dominant belief that Cancer = Death. The term fills people with such fear that the logical components of their brains simply fail. While certainly some cancers, particularly brain cancer, can evolve too quickly and advance too quickly to do anything about (not to mention being almost impossible to predict), these are in the vast minority. In many cases, cancer is no more difficult to live with than diabetes. It can be a managed condition, for a long and healthy life.
So I submit that the notion of whether "Cancer" can be "cured" is actually irrelevant. Any cell at virtually any time has the potential to mutate into a cancerous cell. Most such mutations die without replicating. Some survive and thrive before being killed off by our body's natural defenses. Some grow into tumors or invade organs... Cancers are at least somewhat random in nature, and while much can be done to decrease their likelihood of showing up, there is nothing we can eat or do that will absolutely prevent them. But this does not mean that we should live in fear of cancer, nor that we should assume cancer will kill those who live with it.
What we should do, however, is learn as a culture to implement better critical thinking skills. The huge moneymaking industries that have evolved around alternative cures probably kill more people and reduce the quality of life of those fighting cancer on a relatively high scale, one which is unfortunately impossible to accurately estimate do to a complete lack of accountability. On the other hand, amazing research institutions that are held to the highest scientific and ethical standards have continued to push the boundaries of what is possible. Living, and living well, with cancer is a reality today.