Is it normal for there to be multiple treatments rather than just one?
for small to medium size AN's (typically up to approx 3cm)... the answer is yes.
Will try to help the discussion here.
In doing radio research (regardless of which radiation protocol is being researched ie: Novalis, CK, GK, Proton, Trilogy, etc), there are keys that you want to review in your research. (As Jan noted, suggestion is to go to the ANA Discussion forum home page... top left, use the "Search" option and type in what you seek... LOTS of discussions here in the past years regarding all of these treatments).
In pitting one form to another, you want to research "total accuracy" of each treatment. Novalis publically touts that they have a 2mm total accuracy. CK notes total accuracy of approx 0.85-0.87mm.... approx same for GK as CK.....so, all in all, in doing your homework, keep "total accuracy" in mind. (for me, as part of my decision-making process... total accuracy was key.. if they were going to zap my head, I wanted to make sure the beam hit the target.... but, not to say that Novalis hasn't helped others as well... it most certainly has).
then, you have to look at the AN situation... where is it located? In the IAC? Touching/pressing on the brainstem? current symptoms and potential after affects post-radiation? what is the hearing level at time of radiation and is hearing preservation a key priority to the treatment choice?
these are just a few off-the-cuff notations but the overall picture will have more to contribute to your decision process.
Many here have had many of these radiations... some successful, some not. All of us are more than happy to help answer questions or share our experiences if need be.
Just remember, we are all in this boat together... the oars/paddles are plentiful and we're here to help.
Phyl