Osteosarcoma is the most common bone cancer in dogs, and in most cases, attacks the femur bone. Sarcoma is usually a malignant tumor that arises from the connective tissue of bones and muscles. Out of the three different types of primary bone cancers seen in dogs, osteosarcoma is not only the most malignant, but also the most metastatic.
Primary signs of bone cancer start appearing with mild swelling that refuses to be treated with anti-inflammatory drugs. Later, some elements of lameness may be seen. The lameness becomes more pronounced as the disease progresses. Sometimes the bone is so weakened that the weight of the dog itself can cause a fracture. Bone cancer is very painful and leads to a refusal to eat, and consequently, a significant weight loss is seen in almost all cases.
Bone cancers are relatively difficult to detect and require a host of tests that include X-rays, complete blood profile, ultrasounds and bone scans. A number of other tests are also required to check the level of metastasis that has occurred. The lungs and the liver are the most common organs that are affected by metastatic cancers, causing secondary canine lung cancer and liver cancer in dogs. An ultrasound examination of the heart may also be prescribed, as some of the chemotherapeutic drugs are contraindicated in dogs with heart muscle disease.
In cases where the cancer has affected only the cartilage cells or where the bone cancer has arisen from the fibroblast cells, amputation is a potential cure.
If the lower part of the radius bone is affected, limb-sparing procedures may be adopted. These procedures involve replacement of the bone with a bone from another dead animal, or a metal rod, or a segment of the ulna bone. Sometimes a complicated procedure may be involved wherein the radius of the bone is grown after cutting out the affected piece of bone.
Amputation is the treatment of choice in cases of malignant osteosarcoma. This is done to eliminate the pain that the poor animal experiences. Amputation works only in cases of mild bone tumors, but for aggressive tumors, chemotherapy must necessarily follow to prolong the life of the patient.
The prognosis of bone cancer is poor and the survival time, with or without amputation, varies from a couple of months to a year. If no treatment is to be given, it is better to opt for euthanasia however emotionally disturbing it may be to the pet owner.