Anyone can look into the China Study diet, which is basically a plant-based diet that supposedly helps with many diseases, including cancer. My dad got the book, The China Study, after he was diagnosed with stage 2 CL leukemia 4 years ago and decided to try the diet out for a while before his cancer got any worse and he would have to do chemo. Since then, his cancer has regressed to stage 1 and his white blood cell count has remained steady for the most part.
Take my story for what it's worth, research or read the book if you want, but it wouldn't hurt to try it if you or a loved one has cancer and doesn't know what to do about it.