There is a book out now by Dr Servan Schreiber...In it he talks about the foods that he discovered that held his cancer at bay and now 16 years later he is still in good health.
For anyone, least of all a physician, to say 'these foods kept my cancer at bay' is unethical to say the least, bordering on criminal. All that can be said is that anecdotally 'I eat these types of foods and my (purported) cancer has also not progressed'. Cancer is not a predictable disease. The experience of any given individual from the overall average can vary in the extreme. It may be that some of the foods touted have a clinical effect, and there is good overall agreement that diet can have an important influence on health, but the shreds of evidence from isolated cell studies, etc. that are used here hardly support the grand conclusions he draws.
Eating healthy is very, very good for you. Relying on it as treatment is overstepping.