Morning Kathy. Your ENT is right. Please note that each head MRI has a "total margin of error" (ie: different persons reading the films, giving different measurements, different MRI technology, "slices" of the films/views done differently, etc) of 2mm, thus, you are still within that range... which, I will share this.... is good news as there is NO enhanced growth as of now (and hopefully never!)
You are still VERY soon post radio and honestly, it can take up to 1-1/2 yrs or so to truly see radio's full affect on an AN. So, you just need to hang in there.
The goal of radio treatments on AN's is not shrinkage.... but to kill the core DNA to prevent further growth of the AN (in easier terms, to help "stunt" its growth and prevent future growth).
So, you may not feel great about your ENT noting you are not out of the woods.... but take this to heart.... no enhanced growth on your last set of films, which in my eyes, is great news! Hang tough!
Phyl