Not much until after radiation, other than maintaining good oral care, rinsing, hydration, taking care of any oral infections. Chemo and radiation have just about the same side effects, minus the neck burn, but chemo can even cause burns too, and are more acute, than some radiation effects that are longer term, but so can chemo sometimes be long term. Sometimes you can develop taste and smell aversions associating the nausea from treatment with the last food you ate, and reason some centers give out strong drinks, candies as a scape goat. It's best to eat familiar, maybe not your favorite, non spicy, not hot, non acidic, not sharp textured, not strong flavored foods.

Good luck.