Malignant Bone Tumors
Osteosarcoma is by far the most common malignant bone cancer in dogs. This cancer affects dogs of all ages, with a median age of 8 years. It occurs with equal frequency in males and females. Giant breeds, such as the St.
Osteosarcoma occurs most often in the bones of the front legs, followed (in order of frequency) by the hind legs, the flat bones of the ribs, and the mandible. A common first sign is a limp in a mature dog who has no history of injury. This usually receives little attention until swelling of the leg or a bone mass is observed. Pressure over the tumor causes pain. Fractures can occur at the tumor site.
Chondrosarcoma tends to involve the ribs, nasal bones, and pelvis. It presents a large, hard, painless swelling in an area containing cartilage. This tumor metastazises to the lungs, but is less aggressive than osteosarcoma.
With osteosarcoma X-rays can strongly suggest the disease, but a definitive diagnosis depends on biopsy of the tumor.
Malignant tumors such as osteosarcomas and chondrosarcomas should be treated aggresively. Since these tumors metastasize to the lungs, it is important to obtain a chest X-ray before recommending surgery. The dog should have a complete physical examination, including a blood count and a fine needle aspiration or biopsy of any enlarged lymph nodes.
Partial or complete amputation is the only effective treatment for osteosarcomas of the limbs. Most dogs are able to get around well on 3 legs. Although amputation rarely cures the cancer, it does relieve pain and improves the quality of life. The amputation should be performed at least one joint above the involved bone. New surgical techniques that preserve the leg are currently being done at some veterinary referral centers.
Chemotherapy in addition to amputation increases the survival time for osteosarcoma, but not the cure rate. Radiation therapy may be considered if the cancer is metastatic or far advanced, but is also not a cure. Osteosarcoma of the mandible is treated with radiation therapy, to which it is moderately responsive. Radiation is also used for palliation of pain (reducing pain as much as possible).
Complete surgical removal of chondrosarcomas affords relief, but should not be considered curative.
There is no prevention for this condition.
Please contact your veterinarian if you have questions regarding this condition.
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