Osteosarcoma (Canine)

PetVet
|
Dr. Lauren
|
Parasites Center
|
Cancer Center
|
Flea Center
A-Z
- Anemia
- Arthritis
- Asthma
- Bacteria
- Blood Pressure
- Blood Test
- Digestive Issues
- Breeding
- Cancer
- Cat Scratch Disease
- Declawing
- Diarrhea in Pets
- Dog Flu
- Ear Infection
- Emergencies
- Feline Diseases
- Fleas
- Hairball
- Health
- Heart Condition
- Heart
- Hyperthyroidism
- Hypoglycemia
- Obesity
- Parasites
- Pet Insurance
- Pets and Allergies
- Petvet
- Surgery
- Ticks
- Toxins
- Urinary Tract
- Vaccinations
- Veterinary Care
- Vomiting

| Print

Canine osteosarcoma is the most common primary bone tumor of dogs. It usually occurs in the limbs, but can also affect the skull and jaw, backbone, pelvis and, in rare cases, internal organs. Osteosarcoma is an aggressive cancer that causes severe damage to the bone or tissue in which it develops and also spreads very quickly to other parts of the body (especially the lungs). Medical and surgical treatments may prove beneficial but not curative.

Common name: Osteosarcoma

Scientific name: Osteosarcoma, Osteogenic sarcoma

Diagnosis

Signalment
Osteosarcoma can be seen in dogs as young as six months of age, but is primarily a disease of middle aged and older dogs. The exception is osteosarcoma of the ribs which tends to affect younger dogs (i.e. 4 ¬Ω to 5 years of age). Osteosarcoma occurs most commonly in large and giant breed dogs. Dogs that weigh more than 66 lb are 60 times more likely to develop osteosarcoma than are dogs that weigh less than 22 lb. In large and giant breed dogs the tumor usually occurs in the limb, while in small breed (< 33 lb) dogs the tumor occurs most commonly in the skull, backbone or pelvis.

Incidence/prevalence
The estimated incidence of osteosarcoma in the United States is approximately 8,000 cases per year.

Geographic distribution
There is no known geographic predilection for this disease.

Clinical signs (primary, most to least frequent, scientific term, synonyms)
Lameness (limping). Dogs usually limp on the affected limb due to the pain caused by the tumor. Fractures may also occur due to the damage done to the bone by the tumor.

Clinical signs (secondary, most to least frequent, scientific term, synonyms)
Leg swelling.

Cause (scientific, common term)
The cause of most cases of osteosarcoma is unknown. Some factors that predispose a dog to the development of osteosarcoma include: the presence of a non-healing or very slowly healing fracture, chronic bone infections and radiation treatment.

Organ system affected (most to least affected)
Leg bones, skull, ribs, lungs (usually the metastatic form of the cancer), other organs (rare in dogs).

Diagnostic tests
Biopsy, Radiographs (x-rays).

Differential Diagnosis
Other primary bone tumors i. e. chondrosarcoma, hemangiosarcoma, etc. Tumors that have metastasized to bone. i.e. prostatic adenocarcinoma, mammary adenocarcinoma, anal sac adenocarcinoma, etc. osteomyelitis (bone infection), fungal bone infection.

Overview

Osteosarcoma is the most common primary bone tumor of dogs. There are different forms of this cancer that affect the limbs (appendicular osteosarcoma), the skull, backbone, pelvis, etc. (axial osteosarcoma), the ribs and other organs (extraskeletal osteosarcoma). The most common of these is appendicular osteoarcoma. Appendicular osteosarcoma occurs most commonly in large and giant breed dogs. Dogs that weigh more than 66 lb are 60 times more likely to develop osteoarcoma than dogs that weigh less than 22 lb.

Lameness is the most common sign seen in dogs with osteosarcoma. The lameness may be mild and intermittent at first, but will usually progress to a severe, non-weight-bearing lameness over a period of a few weeks. Swelling is sometimes noted at the site of the tumor.

All forms of canine osteosarcoma are highly aggressive causing destruction of the affected bone or organ. In more than 90% of cases of appendicular, rib and extraskeletal osteosarcoma, the tumor will quickly spread to other areas of the body. The lungs and other bones are the most common sites for metastasis. Some cases of axial osteosarcoma (i.e. mandibular) are slightly less aggressive, but still cause severe local tissue destruction and spread over time. Due to the aggressive nature of this cancer, early diagnosis and treatment are important to maximize survival time and quality of life.

Treatment

Home Care
When a dog exhibits signs of lameness or pain that persists for more than two to three days, the pet should be taken to a veterinarian for a physical examination and, if indicated, radiographs and further tests. Due to the fact that osteosarcoma can occur in an area of chronic bone infection or at the site of a previous fracture that was slow to heal, it is important to have any infection or fracture treated appropriately so that healing occurs quickly and completely.

Professional Care
A physical examination by a veterinarian will help to identify the painful site. Radiographs can then be taken. If the radiographs demonstrate changes that are consistent with a severe bone lesion then a biopsy or more definitive surgery may be recommended. Due to the high metastatic (spreading) rate associated with osteosarcoma, chest radiographs and in some cases radiographs of other bones may be recommended.

Action
A veterinarian will do a biopsy or definitive surgery to obtain a diagnosis. In most cases of appendicular osteosarcoma, treatment involves amputation of the affected limb. In some cases for which an amputation is not feasible, either due to the location of the tumor or the presence of other disease (i.e. severe arthritis, neurologic disease, etc.), a limb-sparing procedure or radiation therapy may be recommended. Due to the high likelihood of spread of this disease, chemotherapy is recommended in most cases after surgery or radiation therapy. Chemotherapy helps to delay the onset of metastatic (spreading) tumors.

Outcome
While it is extremely rare for osteosarcoma to be cured, most affected dogs have an excellent quality of life during and after treatment. The majority of dogs do very well with an amputation and few have significant long-term toxicity associated with chemotherapy.

References/Additional Readings

Dernell WS, Ehrhart NP, Straw RC, Vail DM. Tumors of the Skeletal System. In: Withrow & MacEwen's Small Animal Clinical Oncology, 4th ed. St. Louis: Saunders Elsevier, 2007; 540-582.

Bailey DB. Osteosarcoma. In: Etienne Cote ed., Veterinary Advisor Dogs and Cats. St. Louis: Mosby Elsevier, 2007; 783-785.

Author

Josephine McKnight, BSc., DVM

Dip ACVIM (Oncology)

Editor

Steven Hansen, DVM, MS, MBA

DABVT, DABT

Please note that PetVet should only be used as a guide and in no way should be substituted for licensed veterinary care.