We almost went through a similar situation. We had a cat that stopped eating and appeared very uncomfortable. We took him to a couple of vets, and the second one did an ultrasound (finding a kidney stone that didn't explain everything) and then an endoscope that found what he thought was an intestinal tumor. However, when the doctor operated, he found that what he thought was a tumor was actually a piece of foam rubber that the cat had swallowed at some point and then became lodged in his intestines. He took it out and the cat is now almost back to normal except for losing some of his fat. I was amazed in going through this process all of the medical procedures that were locally available for animals even in a fairly rural area. I wish the best for you "boy" and hope the chemo works.