Dad has throat cancer--proposed treatment extreme?

My 87-year-old father has been diagnosed with throat cancer. He had an initial operation and was told "we got most of it." Recently hospitalized with double pneumonia and a rapid heart rate, he has gone home but the doctors want to begin a 6-week radiation regimen for the throat cancer in which a protective mask is made and he receives a daily shot of radiation. A tube will be inserted in his stomach for feeding during this time. This seems to me to be an extreme treatment for a man his age. I have been told by a friend whose mother had a similar procedure that this can destroy salivary glands and the patient will never feel like eating again or may not be able to eat again. I would appreciate any thoughts or suggestions--I am trying to obtain more information to convince him to get, at the very least, a second opinion on treatment. Thank you so much. This is a wonderful site.