Radiation Therapy
Hi. First of all, I'm sorry that you're having to make this kind of decision right now. It's definitely not an easy one. I just wanted to relate my experience in case it should help you at all.
My situation was a bit different in that my dog was really young (1 year old) and had a mast cell tumor in his groin area. They are thought to be more aggressive in that area and his was removed surgically with dirty margins. Those two facts combined made radiation therapy the recommended follow up. The veterinary oncologist also told me that she thought the surgery combined with radiation therapy would be curative for our dog. We also only lived about 45 minutes away from the radiation facility, so those two thing also made our decision a bit easier.
In any case, our dog had 21 daily radiation treatments, Monday-Friday. He was anesthetized daily for the treatments. He did really well throughout the treatment. He became a bit lethargic about two weeks after the treatment was over and he also had some diarrhea for a few weeks around this same time. He had some radiation burns in the area that was treated, but they didn't seem to bother him much. The whole experience, was really a very positive one with no major side effects or complications. He tolerated the treatment and the anesthesia very well.
All in all, we were very happy with our decision and he is doing really well today...3 years later. I know it's not an easy decision and the answer will be different for each, individual situation and for each, individual animal. Best of luck to you.