One of the tricky things here is that there seems to be some promise to metabolic approaches to cancer therapy, at least for some rare cancers --- but because there is no regulatory or financial barrier to entry for people to devise "nutrition therapy" cancer regimes, it's a space that is absolutely overwhelmed by quackery.
There is, for instance, some actual research generating interesting findings on ketogenic diets as an intervention for glioblastoma and astrocytoma. Unfortunately, "ketogenic diets" are also a mainstay of Mercola-ism, so it's hard to get good lay-reader summaries of what's going on.
"some promise" is very far from "anywhere close to phase I human trials", so, this is not quite that tricky :)
I think a lot of good would come out of:
(1) more awareness of Cochrane Collaboration (& donations to)
(2) prosecutors and the likes of FDA aggressively pursuing people that lead others to reject life-saving treatment, esp. if conflict of interest is present (e.g book sales)
(3) stretch -- teach high school kids basic research evaluation skills (do a search on Google Scholar, consider number of papers, sample sizes, journal quality, author credentials, citations and existence of metastudies). Some version of rough smoke-test for this kind of stuff can probably be automated.
Implied in what you said but worth mentioning specifically when talking about this is that different cancers can respond very differently to the same thing. There is (somtimes quite good) research of the effects of various things on various cancers, just not much (if any) about if combining various non-medical stuff with positive effects could lead to a cure to a particular cancer.
Yes, it's unfortunate the quacks have muddied the waters for ketogenic therapies, but luckily there's enough tantalizing science coupled with a low barrier for self-experimentation (assuming one has a few months+ of relative health) that anyone can attempt it.
There is, for instance, some actual research generating interesting findings on ketogenic diets as an intervention for glioblastoma and astrocytoma. Unfortunately, "ketogenic diets" are also a mainstay of Mercola-ism, so it's hard to get good lay-reader summaries of what's going on.