So sorry to hear this sad news! Unfortunately this is a nasty cancer with a poor prognosis. I have had a few patients with it, they didn't do well. We just lost one last week to seizures, probably from metastasis of the bladder tumor to the brain.
There are two holistic vets I know who are working with cancer and having pretty good success. Dr. Rob Silver in Boulder, CO (303-494-7877) and Dr. Charles Loops in North Carolina (919-542-0442). I know that Charlie works long-distance, not sure about Rob but maybe worth giving a call.
Personally I would not put a cat through a risky and painful surgery, only to have him spend most of the rest of his life trying to recover from it. He would be miserable. I am in total agreement with your decision not to go there.
There are a couple of reasonably easy and harmless things you can do to help him feel a little better for now and might help delay the cancer's progress. First, give him only canned or homemade food (assuming he likes it) because cancer LOVES carbohydrates, and dry food is loaded with carbs. A "CAtkins" diet will starve the cancer and may slow its growth. Second, if he'll tolerate it without a fuss, add antioxidants like Ester C, Vitamins E and A, and nutritional powerhouses like blue-green algae (such as biosuperfood). See
http://www.littlebigcat.com/index.php?a ... atsanddogs
for details on types and dosages. Cancer-fighting takes mega-doses; you can hardly hurt him with these at this point.
I hope your vet is willing to medicate him adequately for pain and stress; other than that, just love him and spend as much time with him as you can. It's so difficult to face these situations, but we owe it to our furry family to be there for them and to make the best decisions we can. Any decision made from a loving heart is never wrong.
Hang in there!
Dr. Jean