Looks pretty clear that a 3-day water fast does a lot in terms of fighting cancer. Cancer cells grow using glucose, not ketones, but if you are fasting, there is no added glucose for cancer cells to use. Also, the lack of additional protein undermines tumor growth.
A long water fast stimulates autophagy, which may mean the actual destruction of cancer cells.
A long water fast also simulates the immune system, which may be a key player in fighting off cancer. There have been many authorities assert that long fasts are beneficial for those doing chemo, largely because of this effect of restoring the immune system, which otherwise gets whacked on chemo.
The Keto diet with low carbohydrates and moderate protein might be the best choice for a cancer patient. Again, low carbohydrates minimizes the amount of glucose available. so cancer cells “starve”.
There’s quite a bit of evidence that mushrooms have the effect of minimizing blood vessel growth. This can help with cancerous tumors as these tumors need blood vessels in order to continue growing.