I had to say goodbye to my 12 yr old ‘Fred’ last month after he had a goofball sized tumour in/on his spine at the injection site (ironically for the anti cancer drugs)
Worst and hardest choice ever to take him for his final trip. I totally failed to MTFU.
Sadly you’ll know when it’s right, and the vets are sensible with their advice I found – yes surgery was an option, but you’re delaying an inevitable fate, while causing more discomfort :(