You are in an area many find themselves in. As lay people trying to decipher what is the best choice. As to the percentages you have quoted I’m not sure where those came from. Most of this is unknowable. Even if it were, we are all unique biological entities with very different genomes, and therefore biological response to treatments. Bottom line you are not a statistic and statistics do not apply to any singular individual.

I am curious about MSKCC’s stating that they would limit radiation to the neck. They are one of the best institutions in the world, with lots of experience and a deep bench of great doctors. But the experience is that recurrences are usually near the original focal tumor. Most of those are related to either dysplasia in the margin, or dysplastic cells in the nearby tissue finally moving to malignancy, around 18 months or more out from treatment. This is a by product of field cancerization.

I would want to understand their thinking on that before going further. Proton beam radiation is certainly more targetable and less damaging to surrounding structures. I’d be less concerned with its impact than getting all areas covered that might pose a future risk.