At that age, I think treatment is almost cruel when there is little chance of a "cure" and long life. ((hugs)) No one can decide except you but I'd go with the vet's suggestion.
The vast majority of TCC cases are treated with medical therapy, i.e. with drugs. Two different drug protocols are used most often in the standard care for dogs with TCC. The first treatment protocol is to give a drug called piroxicam, or a piroxicam- like drug by itself. Piroxicam is a type of drug called a nonsteroidal antiinflammatory drug or “NSAID”. NSAIDs block the cyclooxygenase (cox) enzyme, and are also referred to as “cox inhibitors”. Cox inhibitors include piroxicam, aspirin, ibuprofen, naproxen, Previcox, Deramaxx, Rimadyl, and others. There is an interesting history behind the use of cox inhibitors for the treatment of TCC in dogs. Veterinarians in the Purdue Comparative Oncology Program became interested in piroxicam several years ago when it was being used for pain relief in dogs with cancer, and unexpected remissions were noted. Two of the first dogs treated (one with metastatic carcinoma, one with undifferentiated sarcoma) had advanced cancer, and these dogs had remission of their cancer when receiving piroxicam, but no other treatment. This has led to numerous studies of piroxicam in animals with cancer at Purdue. In 62 dogs with TCC treated with piroxicam, the tumor went into complete remission in 2 dogs, decreased in size by > 50% in 9 dogs, remained "stable" in size (<50% change) in 35 dogs, and increased in size by > 50% in 16 dogs. The median (“average”) survival was 195 days.