Hi,
Radiation techniques have significantly evolved over the past decade, making this treatment much easier and safer.
If the opposite salivary gland can be spared, there will be tolerable side effects.
You are right in identifying nutritional status as one key parameter which will determine his tolerance of further treatment.
He must eat well, as much as he can tolerate.
All the best, and God Bless!
I forgot to mention that 90% of the tissues were removed according to the docs and there were no other tumors in the CT scan.