Hi Zoe,
Welcome to the forum, and sorry to hear about the AN. I hope you listen to what Jim and others have said, and take enough time to find out what your options really are, and what the pros and cons are, and what doctors are available, before you make your decision. Don't rush into anything.
I have to comment on the "radiation never leaves your body" statement, it is just the way I am. I'm sure there was some misunderstanding, because the statement doesn't make sense. Cyberknife radiation treatment, for instance, uses x-rays, just like a dentist x-ray or a mammogram does. The x-rays pass right through your body and out the other side immediately.
While radiation treatment is not for everybody, it is certainly a reasonable choice, and I would hate for you to pass up considering it based on misinformation or a misunderstanding. Maybe the doctor meant that the radiated AN itself is still inside you? That is true; it just withers and dies, but is not physically removed.
Any way, take care,
Steve