Lori,
I am in tears just reading your message. I've had the same thoughts. I don't think anyone can tell you (or me) with any certainty. My Kacee's tumer takes up probably 2/3 or more of her bladder. She has the occasional accident, but I have learned to force her to go out frequently (even getting up during the nite) and that has helped with the puddles. I don't know if the piroxicam and graviola have done anything to the tumor and I have not had her re-checked. My reasoning is that the cancer is not going to go away so why put her thru any vet visits. I will keep giving her both because it doesn't seem to be hurting her, and the graviola seems to give her more energy. As long as she is not in pain, still wants to play (even if it is only short periods of time), is still eating and still excited about "treats" she is going to stay with me. The vet had told me that eventually the tumor may get so large it will stop her urine flow and that would be the time to "move quickly" as he put it. Its just one day at a time. Sorry I have no answers, We all have to do what we feel is best for our babies and ourselves. Every case is different. Just know we are here for support and kind words.
Karen