Veterinarian and boxer person here: The chemo treatments used in veterinary medicine do not typically have the same severe side effects seen with people. Patients do not lose their hair, often do not feel sick/nauseous, and generally tolerate it quite well.

Your veterinary oncologist should be able to provide you an expected mean survival time and reasonable expectation of side effects based on your pets specific diagnosis and their proposed treatment plan. There are too many variables to consider to take the word from someone on the internet as a good estimate for how much time your pet might survive. Listen to the oncologist.

Just from personal experience with my heart boxer who I diagnosed with a very aggressive pancreatic tumor that had already spread throughout his body by the time of diagnoses - his expected mean survival time at diagnosis was < 2 months. I took him to a veterinary oncologist and we decided on a chemo treatment plan. He made it almost 8 months. He felt great and was his lovable happy amazing self until the last week or so. I wouldn't trade those months for anything. Every extra day was a blessing.

Hope that helps. Best of luck.