My personal opinion is that when diagnosed with cancer the biggest dietary change should be towards really eating healthy. I know this isn't what you asked, but I do think it's important, the most important. Guiding a diet away from supplements to preserve, enrich taste, texture, etc. just can't be good for a body needing all of its attention on destroying an invader.
I've been diagnosed with cancer 5 times and feel it's important that the doctor have a solid foundation to work on. To date it's worked for me, I'm in remission from an incurable and plan staying that way if I can .