Mr. Otworth paid about $25,000, all told, for Tina’s treatment at his local veterinary clinic and at North Carolina State. He also wrestled with the tough questions that pet owners face in deciding whether to go ahead with late-life treatment. Will the pet suffer unduly? Will treatment give it a good quality of life, or merely extend it?

“I wondered if I was doing this for selfish reasons,” he said. “As someone who underwent cancer treatment, I asked myself, ‘If I were a 10-year-old dog, would I want to go through this?’ ”

Some pet owners decide on treatment and then, after writing out the checks, have sobering second thoughts.

Chemo-therapy and bone marrow transplants for dogs? I don’t know how I feel about this.