Puppy Snuggles: The Question

Bovver had his CBC's on Wednesday after his third round of chemo and is still doing great, but his lymph node seems to have grown in size. After his first round of chemo his lymph node almost went back to where it was before all of this. It gradually grew a little bigger, but after the second round it went back down quite a bit again. After this third round, unfortunately, it has grown larger than it ever has. His cancer is mutating so quickly that the chemo is no longer effective. Going in to this we thought that he would have no trouble with this treatment plan and would go into remission for a few months after he was done with the chemo. Sadly, that is not the case for our boy. His oncologist just told us that he's unlucky. It's already rare to have both Myasthenia Gravis and Lymphoma, its even more rare to have T-cell Lymphoma, and it's even more rare that he was not able to go in remission with the CCNU chemotherapy treatment plan. 

Eric and I have a pretty big decision to make.  Do we continue with another type of chemo (Doxorubicin), or do we stop his chemo all together?

The doxorubicin is considerably more expensive than his original treatment, but the chemotherapy has really kept his Myasthenia Gravis at bay, and I'm afraid that if we stop treatment it will come back and our boy won't be able to get around anymore. He has been doing so well lately and it's really hard to imagine him going down hill again. We saw how quickly it can happen and that is pretty terrifying. We really want to make the best decision for Bovver. He has been doing so well with chemo and has had very little side effects. We've spent so much time, money and love that I'm not sure I'm willing to stop fighting just yet. We are obviously just prolonging the inevitable, but when do we call it off? How many trips to the vet are too many for him? How many pills and IV's are too many for him? How much money is too much? I don't have any answers just yet. All I know is that we will get through this together.