Foods have a rating on the Glycemic Index, according to how long or how quickly it takes them to metabolize into usable celluar energy, called glucose or blood sugar. The bottom line is that to help yourself, without helping the cancer, you need to eat foods that are LOW on the glycemic index (i.e. slow burning/complex metabolism into cellular energy).
Think of it this way:
quick burning, simple sugars & refined flours = insulin spike
regular and/or frequent insulin spike = insulin resistance
insulin resistance = impaired immunity AND excess circulating insulin growth factors
excess circulating insulin growth factors = food for cancer cells