I know this is nothing but hearsay, but it sounded at least possible when this was first told to me.
So I understand those who will want to take it with a grain of salt.
About 25 years ago someone had told me he had heard of a lubavitch chassid who had been diagnosed with Cancer.
I was told this chassid who did not eat much to begin with, cut his diet even more to where he just had a small can of Sardines each day and cured himself by starving the Cancer out.
This is not to say this would work for everyone, just that it worked in his particular case.
But my point here is that according to the one who told me this (I don’t remember who after all these years, but someone in Crown Heights, might know this story, if it’s true.), said it was accomplished through a strict diet but ###not### a Vegan or Vegetarian diet.