Can radiation therapy lead to carotid artery blockage?

Not likely: Radiation causes vessel injury and small arteries are damaged while other vessels are created. Arteries can get harder and scarred. In a larger vessel like the carotid these changes can take place but to completely block is not likely. There would have to be very high levels above normal such as in a case perhaps retreated. One more likely worry in that situation would be carotid blowout.

I do not agree: Radiation to the head and neck area could potentially increase the risk for carotid artery disease years after the treatment. I routinely discuss this risk with my patients whom are being treated for a head and neck cancer. Unfortunately, the treatment with radiation is necessary for their disease so the risk of treatment is outweighed by the benfits.

Depends on age: Chang in a 2009 paper suggested that in a study scoring atherosclerotic plaques in the carotids in patients after XRT that while patients less than 41 at the age of tx had a higher correlation those patients older than 50 actually had a negative correlation with plaque scores.