John - ORN is (I think) Osteo-Radio-Necrosis. Its a dangerous degenerative condition that can occur in radiated tissue. I don't know the mechanism, but small sores or injuries do not heal, rather they grow very large and become threatening to surrounding tissues.

ORN in the jaw can cause the complete loss of the entire jaw. The radiation so damages the blood vessels that they cannot supply injured sights with healing fluids - precipitating the catastrophic loss of tissue. Its really ugly stuff. It is the fear of ORN that keeps most of us from risking any surgeries in the radiation field. It can be risky.

Hyperbaric Oxygen treatment is a mechanical method to attempt to oxygenate damaged tissue. It is, I believe, the treatment of choice to try and stop ORN from advancing.

Please seek better definitions of both of these terms. My knowledge is limited, and you need solid information about both of them. Your doc can help you. Hope this helps a little. Tom

SCC BOT, mets to neck, T4.
From 3/03: 10wks daily multi-drug chemo,
Then daily chemo with twice daily IMRT for 12 weeks - week on, week off. No surgery. New lung primary 12/07. Searching out tx options.