As mentioned, getting a 2nd or even 3rd opinion at a top CCC may be beneficial. Although each situation, and personal preference is different, I had radiation 5x to my neck. Four were after some radiation oncologists didn't want to do more due to dose limiting toxicities after my initial 70Gy, bilaterally, for oropharyngeal cancer, but found others who would, safely, and then some, using different types radiation and techniques. My last was with Proton Therapy, and there was a 20% chance of carotid blow out, even with it already removed, but still went ahead, and faced other risks from other surgeries, but they were all better than the risks of not doing anything. One RO said the carotid artery is very resilient.

Good luck.