What cumulative dose would you allow the pharyngeal carotid to receive for a course of reirradiation for a retropharyngeal node?

No dosimetric data available. I don't use a carotid OAR in my cases, and just ensure the disease is appropriately covered, while limiting cord/brainstem primarily.

From the literature, highest risk cases are those with skin involvement (ie tumor from skin to carotid). Risk of 1-5% for carotid blowout.

HyTEC publication on SBRT and carotid in reRT setting: Grimm et al., PMID 33583641.

I agree--there is no established dose. I have also previously discussed the matter of attempting to spare the carotid with disease that is subjacent or encasing the major vessel. The vast majority of the data in the publications from UPMC, including the multi-institutional review (MIRI), did not spare the carotids. As noted above by @Dr. First Last the HyTEC paper which gathered and modeled the larger worldwide experience is a valuable reference. It is important to note, that when performed corr...