Hi @gareygraham and welcome to the head and neck cancer group. Although I did not have cancer that far down in the throat, nevertheless my voice was affected by the radiation so much so that I sought out help from a speech and hearing pathologist. Camera down the throat and all those fun things revealed little. I resolved to sip water as I spoke and face the fact I no longer possessed the "stage" voice I once had. I often worked in noise environments instructing others. Had to find a different way. As with you, the voice changed and became hoarse as the day went on.
How long ago did you finish up radiation treatments?