Cindi, Don be surprised if the vet comes back and tells you specialists say it doesn't work. There are few studies and not enough is known about it.
All I can suggest is to bring in copies of the few documents there are on it. Highlight the positive statements in it. Something I also did was to mention all her symptoms and that the medicine could help those over anything else. Which for Olive it did. That was my main argument. And to hopefully level out her blood sugar. My other stance was there was nothing to lose in trying it and we had everything to gain. It's her only option of being more comfortable. Besides the vet that I used for years, I took her for 3 other consults/2nd opinions with other vets, spoke to 2 other vet practices on the phone. Emailed the neurologist who does the removal surgery. Spoke with endocrinologist he recommended but doesn't treat acros anymore. It wasn't easy and at times disheartening and sometimes I got downright angry that no one would help us. Olive was miserable and I don't know if any amount of insulin would have made her comfortable. Insulin alone (as I understand) doesn't help the pituitary tumor from secreting the hormone that causes all discomfort, pain and damage it does.
I did have to change vets to get it.
If you really want to try it, then all I can suggest is to keep trying. Have realistic goals (slow down tumor activity, make kitty more comfortable). Don't wait to long before asking vet if they looked into it. Keep on them but gently.