Just like with people, each animal reacts differently to chemo. Some do very well and others don't. It's up to each owner to determine whether or not the side effects that the animal suffers is worth the potential prolonging of life. For some animals, the side effects are short term, but their lives are prolonged by several years. For others, they side effects are extreme and their lives are only prolonged by months.
One of the racing dogs from the greyhound track was brought in when he was attacked by 8 other dogs. He had severe wounds and the track wanted to euthanize him. We contacted the local greyhound rescue and they agreed to absorb all of the costs associated with his medical care. Thousands of dollars and several days of continuous nursing care later, he went to a foster home until his forever home could be found. There are countless heros in this story, as so many "faceless" people are involved in rescue organizations.
Over the course of two months, a total of 12 kittens were brought in by people who found them alone and seemingly without a mother. 2 of these kittens had no hope of surviving. All of the other kittens were fostered by various techs during the evenings, foresaking sleep and sanity so that these young lives could be saved. I consider each of these people to be heros. You never realize how difficult it is to have to get up every 2 hours to feed kittens and stimulate their urination and bowel movements until you've done it for an entire month.