He's had three extra years of happy existence. Theoretically, there would be a line that you would draw, but you don't know until you get there. We've had success with our treatments. But that's me. Someone down the street might not want to do that to a pet, and I would respect that opinion.
Many owners have limited finances, which can come into the decision-making process.
Or the owner may have other reasons for not wanting to pursue treatment. Treating cancer is often expensive. I truly feel it is an individual owner's decision, but people need to know that there are options. For some owners, the fight with cancer may end with helping their pet die. All owners should realize that the gift of euthanasia is a gentle, humane way to end the life of a cherished animal friend.