Every situation is unique in its own way, but speaking from my own experience, yes they can perform surgery on a previously radiated area. And, as I have recently learned, they can also do IMRT again. I had chemo/IMRT last year for cancer of the tongue. They radiated my mouth and neck nodes March - May of 2006.
I have recently experienced a recurrence/mets to a jugular lymph node, and I just had a neck dissection on the right side about 3 weeks ago. Now I am also preparing to begin IMRT and
Erbitux. I asked this same question because it was my understanding IMRT was a 'one time shot' and couldn't be done again.
My radiation oncologist explained that while it's not optimal due to the tissue damage possible, in my case RT is the safest and best option, as there is some cancer on my carotid artery they couldn't get in the neck dissection, and surgery would be risky. My RO explained he is carefully mapping out this second course of IMRT to consider the previous mapping from my first round (specific locations and intensities of the RT delievered), to determine what I can tolerate now in the second round.
As I'm sure you know there are not many absolutes like "never" or "always" with this desease or the treatments for it. But to answer your question, yes, RT could be administered again if the circumstances allow and surgery is possible even if RT was previously administered.
I'm sure there are countless issues that go into the doctors' decisions for these things - like healing in-between (such as how long it's been since radiation, etc), the extent of the disease, the overall health of the patient, etc. So, what treatment methods can be used for your case may be different than those for somebody else's case.
I hope that helps a little.
-Steve J.