I had a 12 mth old Boxer and she starting limping and I realised that there was a lump on her leg, say where our ankle is and it started getting bigger quickly..took her to our vet and he did a biopsy it was Osteosarcoma (bone cancer) and a very aggressive form, I was informed..and that longterm there was no real solution, it would have just been prolonging her life a little, but in my eyes no real quality..
Vet gave me all the options and I came to the decision that I wouldn't go through chemo persolly and made the decision to have her pts, but chose to have it done at home so it would be more peaceful for her, as she was a rescue and had enough crap in her short life....
wish you luck with your baby..