I am a nutritionist and yes, I have. And my bottom line is that the same healthy and balanced diet recommended for all people is the one that is best for cancer patients as well. There are no foods that either cause or prevent cancer. A substantially vegetarian is a good thing, but for many people the vegan protein choices are too limited and there are many micro-nutrients we need that are only available in animal food.
Oncologists are not dietitians. They deal with patients who have lost their appetites due to chemo affecting the way food tastes. So naturally they will say eat anything and I agree with that completely while in active chemo treatment. The whole organic thing is a different issue altogether. Some foods easily absorb pesticides but most don't. So from a health standpoint, the organic movement is more of a political and environmental issue than a health issue.
Avoiding sugar is impossible because everything we eat is converted into sugar since that is the only form in which our bodies can use for fuel. What nutritionists say is avoid adding additional refined (i.e. overly processed) sugar....big difference. Any meat in moderation is fine. Some foods are fine raw and others can be harmful eaten raw.
I think the most confusing aspect in the food arena is trying to separate hype, politics, and fads, from solid science based nutrition. Food is a basic necessity. Usually when anyone starts throwing around words like organic, natural, raw, super, magic, etc. it becomes more about hype and less about logic..