Keep in mind that dogs are usually euthanized due to the pain in the affected bone. Treating the pain successfully will allow a dog to live comfortably and extend life expectancy by virtue of extending comfort. There are two ways to address the pain: amputatating the limb and palliative radiotherapy (usually combined with periodic bisphosphonate infusion treatments).
For most patients, there is one tumor on a leg and no visible tumor spread in the lungs. These are the patients with the best potential results and they are good candidates for amputation. Patients with a lot of arthritis in the other legs or with tumor spread evident in the chest already are probably not candidates for amputation and it may be more appropriate to keep the leg and simply relieve the pain with radiotherapy.