As a dietitian, I would strongly recommend that you talk with one of the dietitians at Mayo or if you are not at Mayo, talk with the dietitian at the hospital you are being treated at. There are some great resources on Nutrition from the American Cancer Society. I asked for a consult with one of the Mayo dietitians and got some excellent information. If you are at the clinic they do a nutrition workshop at least weekly.
I make sure I ate a variety of foods from all of the different food groups and did not do a special diet. The biggest challenge was that I had some taste changes. I also ate small frequent meals.