I had a radical neck dissection in 2011 six months after radiation. Had two more neck dissection surgeries thereafter, same side, one including HD-IORT, and a pectoral flap, then Chemoradiation for 6 weeks. I really have no problem with pain, but lack of feeling on my neck, and a little mobility impairment raising my left arm fully overhead, and no tissue failure. As far as Reirridation, it is susceptible to more tissue failure, healing problems, nerve damage, carotid blow out, than unradiated tissue, but the pec flap brings in radiated tissue there under the chin if you need it there. The other areas can be Reirridatied, and dosage depends on how much radiation you had before, and where you received it. To kill most cancers in the H&N it has to be above 50Gy. Unacceptable toxicities begin after 75 Gy, but there are ways to deliver more with split daily radiation, brachytherapy, IORT, IMRT, IGRT, and stereotactic radiation like Cyberknife, and is being done more often depending on your doctors or hospitals experience. For reiiridation it will be more specific, and depends on the structure radiated what are the acceptable levels, and risks involved. I hope this helps.