How many hours should i put between meals and a radiation session of the pelvis to prevent nausea/vomiting?

I would suggest: At least 4-6 hours if possible. Anti nausea medicine may help as well.

Dr Khanna agreed

Pelvic radiotherapy : Rarely causes nausea or vomiting (upper abdominal, stomach or pancreas, even the old inverted y in lymphoma may). We usually suggest a light, non-fatty meal before - dry cereal or toast, water or tea, but for pelvis therapy, one needs to worry about diarrhea - avoiding fresh fruits and vegetables.

Dr Hochman agreed

Not a clear answer: Pelvic radiotherapy does not commonly cause nausea or vomiting. This comes more from upper abdominal radiotherapy with or without chemotherapy. The highest side effect risk from pelvic radiotherapy is diarrhea which can be avoided with dietary restrictions such as avoiding roughage.