Hi Rich and welcome. Good to have you here.
You will find much info re: all kinds of radio-treatments and lots to learn. If you find yourself overwhelmed with the info, please take a step back for a day or 2 before your research continues. Lots to learn.
There are many variables that a radio team has to look at to determine what will be the best course of radio-treatment. The size of the AN, the exact location of the AN (ie: is it pressing against the brainstem, does it stick out of the canal, etc). Other factors are balance and/or hearing issues, etc.
On these forums, we have heard of 1 day, 3-5 days.... to 25-30 days. It all depends on the course being done and how applied. For me, I had 5 days (30Gy of radiation total) over 5 days and I do know of many more that had the same..... so, 5 days is not unusual. Many here that had "FSR" (as you note, possibly via the Novalis radiation delivery) typically have from 35-30 days (I bet my co-hort in moderator crime, Jim Scott, wiil chime in as he had FSR delivered over approx 25 days).
There are many expert radiation teams across the US. I'm not sure where you are located but by mentioning Dr. Lederman, would it be fair to say you are on the east coast? If yes, there are many terrific radio treatment teams up and down the east coast. Being located in Boston, I"m kind of partial to the teams here locally but there are certainly many others on the east coast worth researching as well.
Anyway, based on what you shared, this is just a quick insight. Hope it helps.
again, welcome!
Phyl