Dog bone cancer occurs mostly in middle-aged and geriatric dogs, and usually occurs in the legs. Larger breeds are more vulnerable to dog bone cancer. The most common type of dog bone cancer is ostesarcoma, a tumor that grows inside the leg bone; less common types include squamous cell carcinoma and synovial cell carcinoma.
Diagnosing Osteosarcoma
Osteosarcomas, or tumors inside the bone, can grow in any of your dog's bones, but they usually appear in the limbs. These are called "appendicular osteosarcomas." They destroy the bone from within, causing the dog more and more pain. Lameness sets in within one to three months; swelling occurs as the tumor grows larger.
Tumorous bone is weak and breaks easily. These kinds of breaks, which never heal, are known as "pathologic fractures." Dog bone cancer is usually diagnosed when a pathologic fracture occurs.
Bone tumors are usually diagnosed by X-ray. Characteristics of ostesarcoma include:
- Lytic lesions, or areas where the bone appears to have been eroded.
- Sunburst patterns, in which the growth of the tumor creates a corona effect on the X-ray film.
- Pathologic fractures
- Osteosarcomas do not cross the joint to other bones.
A biopsy can provide irrefutable proof of dog bone cancer.
Other Types of Bone Cancer
While osteosarcomas account for most types of dog bone cancer, there are several other types of dog bone cancer that should be checked for it osteosarcoma is ruled out. They are:
- Chondrosarcoma, which is a tumor of the cartilage. Some vets believe these tumors don't spread as fast as ostesarcomas. They are common on flat bones, like the ribs.
- Squamous cell carcinomas occur on the outside layer of the bone, known as the periosteum. These tumors also spread slowly, and tend to occur in the jaw or toes.
- A synovial cell carcinoma occurs in the joint capsule lining. They affect the bones on both sides of the joint.
Treating Bone Cancer
Dog bone cancer can be treated with surgery, radiotherapy, pain relieving drugs and chemotherapy. If the cancer occurs in a limb, amputation can relieve the pain of the cancer and, if the cancer has not yet metastized to other parts of the body, possibly stop the spread of the disease. Limb-sparing surgical techniques may be used to replace the diseased part of the bone with a graft of healthy bone.
Chemotherapy can help most dogs live as long as one year after diagnosis if the cancer has spread, though survival rates beyond one year are quite low. Chemotherapy treatment lasts about three or four months and owners can expect dogs to display lethargy and nausea for a day or two after treatment. Chemotherapy for dogs does not cause hair loss. Typically, dogs with bone cancer can expect at least six months of quality life with chemotherapy.
Radiotherapy may be used to ease the pain of cancerous tumors. Pain relieving drugs, like aspirin, carprofen and etodolac can provide initial pain relief but, in the long term, many dogs with bone cancer are euthanized as a last resort pain treatment.