As Kelly and Paul have posted, the old "maximum radiation" story is not necessarily true. Two factors are important:
First the total number of GY in radiation he has received. They used to say 77 was the max, but Kelly had 190, I had 137 and Paul 132. Second, the fields already radiated. It took weeks for my Radiation oncologist to compare the prior radiation fields and plot a new one that would not cause too much necrosis.

My RO is Dr. William Harter at Georgetown University Lombardi Cancer Center in Washington DC. Could not hurt for your doctor to give him a call and discuss this. My neck is pure leather also on the left side. The key is to go to place that has something like CyberKnife which can focus the radiation more than the regular IMRT sites.
Charm