[MontanaRott]

It is indeed a very personal and individual decision. Our Frenchie was diagnosed with Lymphoma this summer, because of his age, and prior history of health issues, plus how advanced the disease was, we elected not to treat him with chemo. He took a course of antibiotics and prednisone and that was it. He was happy and himself for a bit, and we watched him, and listened to him very carefully. When he no longer did the things he loved, we let him go.
I think one really should take prior history, age and general health of the dog in question into consideration when making the decision. Not to mention one's financial situation. As much as we love our dogs, we cannot afford to drive ourselves bankrupt to save them, just do what we can afford to do, within reason, and don't drive ourselves nuts with the what if's.
I am sorry you are going through this, it is never easy.