Golden retriever with lymphoma died.

My golden retriever was 125 pounds (all muscle) and enjoyed perfect health for all of his 10 years-that is, until about one week ago when he was diagnosed with stage 3 lymphoma; virtually overnight his lymph nodes went from being more or less unnoticeable to being the size of golf balls. I brought him to an animal oncologist who diagnosed him with stage 3 lymphoma (b-cell involvement); his blood was clear. We decided to forego chemotherapy, give him the prescribed 60 mg prednisone, and look into natural treatments. We were told that his stage we could expect him to live about 1-3 months on the prednisone. Unfortunately we did not have time to do any of the research we'd intended to do on natural treatments: after enjoying about 2 good days on prednisone (appetite returned, and was able to go for walks, and lymph nodes shrunk to normal size, and stayed so until to the end), his health rapidly declined. First his appetite went away; we resorted to feeding him from a dropper. Then his desire for water went away. He would sometimes drool. His legs became so weak that he could barely walk, and on his last day his hind legs seemed almost paralyzed (he had never had hip problems). His stomach became distended. On 1/2/2011 in the middle of the night my dear pet placed his head upon my knee, looked deeply into my eyes, vomited a large amount of blood, and passed away about 30 seconds later. He will be sorely missed. His vet and others I've spoken to seemed somewhat surprised that he went so soon and in such a manner. I have no doubt that the lymphoma diagnosis was correct but the time of his death (within a week of diagnosis) and the way he died does not match what I'd been told to expect, and what I've read online. Could it be that although he had lymphoma, he died of something else altogether? Is it paranoid on my part to speculate on possible poisoning. The day after his diagnosis, on his walk, he ate something he found outside. I barely got to see what it was but it looked like it could have been a chunk of dark bread. It made a crunching noise. Could this have been rat poison? I know his death was almost certainly cancer related but I can't get this out of my mind. Does his death sound like a lymphoma caused death. Thank you so much.