Keep citrus fruit to a minimum. Yes, we know how the television ads state that orange juice fights cancer, but that is prevention only. Citrus puts your body into an acidic state. Nearly all of the cancer institutes we've talked to during our research said the same thing: if you are battling cancer, keep your citrus to a minimum. Get your vitamin C from supplements.
I might add that another reason to not consume too much fruits or fruits juices when actively fighting cancer would be the high sugar content of most fruits. It is probably a good idea to keep your ratio of vegetables to fruits about 4 to 1 or higher.