my aunt was also cancer free for like 6 months then the cancer was back now she has to decide if she does the treatment and lives her last months like a zombie( with a low chance of survival) or if she will try to enjoy her last months and make peace.
While i understand that people love their pets, id lay down my life for my cats...
Theres a point where medical treatment is not worth it. Cancer treatment even for dogs costs a **** ton of money, almost always debilitates them in some way for the rest of their lives, and generally shortens their lifespan. Granted, its better than dying of cancer, but hell man, couple hundred grand and a remaining mediocre lifespan, with a decent chance of it not being successful, id rather have my dog put down.