Benfry

Cancer on the side of the tongue is often removed surgically. Cancer at the base of the tongue is usually treated with radiation and chemotherapy at first since surgery on the base of the tongue is traumatic. While I can still talk, I can't swallow after my base of tongue surgery.
But your Dad has surgery scheduled in less than a week. You will have to either postpone that or really hustle to get a second opinion. We usually recommend a Comprehensive Cancer Center (CCC) but your Dad's doctor should be able to round up a radiologist to give an opinion.
However, if your Dad's fear is his speech, if he keeps his larynx, he will be able to talk but he may very well have a speech impediment after the surgery. I do.
A recurrence does require drastic action but sorry I can't give you an answer.
Charm