Eventually it will be more than just your voice affected as cancer continues to grow and spread. At age 80 the question is what to do as a quality of life issue. There are alternatives to standard cancer treatments which can be explored such as a shorter radiation regimen and/or drugs such as Keytruda. Ask your Oncologist and at the same time, ask your Oncologist what they would do at your age.
For me, that's ten years out yet. Would I go through what I went through twenty plus years ago at that age, or even at my age now? I can honestly say that I doubt I would go down the same road. Doing nothing of course will kill me, and not likely gently. I would try a lighter sentence. Certainly I would insist on proton radiation as opposed to photon.
No one here of course can tell you what to do, only suggest. But I think when we are actually in your shoes, we will only then know the path you are on.