Osteosarcoma

Liaison: Liz Swearingen

Osteosarcoma (OSA) is a malignant tumor of the bone (bone cancer). It can develop in any bone, but occurs most often in the limbs, near the shoulder, wrist or knee.

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Osteosarcoma (OSA) is the most common malignant bone tumor in dogs, but only accounts for 5% of canine tumors. It can develop in any bone, but 75-85% of canine osteosarcomas occur in the limbs (appendicular osteosarcoma). It is most common in large and giant breeds, developing at middle age or beyond, but it can occur at any age.

Osteosarcoma is painful and frequently causes lameness. It starts within the bone and destroys the bone from the inside out as it grows. Swelling may also be seen as the tumor grows and replaces normal bone with tumorous bone. The tumorous bone is weaker than healthy bone and can break easily (pathologic fracture) - this type of break will not heal.

Osteosarcoma is aggressive and highly metastatic, most osteosarcomas have already metastasized to the lungs or other bones when diagnosed.

Signs and Symptoms

The signs and symptoms depend on the location of the tumor:

Limbs:

Lameness due to inflammation, fractures or microfractures
Swelling or mass at the site of the tumor, sometimes painful

Lower jaw or orbital (eye socket)

Difficulty swallowing

Skull or vertebrae

Neurologic deficits

Pelvis

Difficulty defecating

Causes

The exact cause of osteosarcoma is unknown. The tumors are often found near growth plates, so factors promoting rapid growth rate and bone turnover may be involved. In animal studies, several viruses (polyomavirus, SV-40 virus and type C retroviruses), fluoride, and metabolites of the insecticide diflubenzuron, have been linked to osteosarcoma.

Risk Factors

Dog is a large or giant breed
Previous fractures
Chronic bone infections
Foreign bodies such as metal bone implants
Mutation in p53 tumor suppressor gene
Spaying or neutering prior to one year of age (see link below)

Cooley DM et al. 2002. Endogenous Gonadal Hormone Exposure and Bone Sarcoma Risk. Cancer Epidemiol Biomarkers Prev 11:1434. three bonesrating

Diagnostic Tests

Diagnosis may include the following:

Physical exam to rule out other causes of lameness
Orthopedic exam to rule out other causes of lameness
Neurological exam to rule out other causes of lameness
X-rays of the suspected tumor
X-rays of the lungs to look for metastases
Bone biopsy to definitively identify the tumor
Abdominal ultrasound (to look for metastases)

Other types of cancer and infection must be ruled out.

Chondrosarcoma - a tumor of the cartilage
Squamous cell carcinoma in the external coating of bone
Synovial cell sarcoma - a tumor of the joint capsule lining
Infection of the bone such as Coccidioidomycosis, caused by the fungus Coccidiodes immitis

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Treatment plans for osteosarcoma may be either curative or palliative (relieve/lessen pain without curing).

If the intent is to attempt a cure, the tumor must be removed either by amputation or, when possible, limb sparing procedures. Surgery may be followed by chemotherapy to reduce metastases. Because most tumors have already metastasized when diagnosed, cure is difficult.

Palliative care typically includes radiation and pain medication.

Artemisinin is an herb that has been shown to kill some cancer cells in the laboratory. Anecdotal reports claim that it can stop the growth of osteosarcoma in dogs, but peer-reviewed scientific research has not yet been published.

Prognosis:

Prognosis depends on many factors including the dog’s age (it is more aggressive in younger dogs), size of tumor, location of tumor, blood levels of alkaline phosphatase, and presence of metastases. Survival times vary greatly. Median survival times of 3-18 months have been reported, depending on the location.

Management

If amputation is required, most dogs do very well on three legs, not realizing that they are disabled!

Help for Tripod Dogs onebonerating

References

Osteosarcoma, caninecancer.com one bonerating

Canine Osteosarcoma, marvistavet.com two bonesrating

Support Groups

Bone Cancer Dogs, Inc.

Canine Cancer Awareness Organization

SCARF-Sponsored Research

MAF Grant D19CA-064: Synergizing Radiation-Induced Immunogenic Cell Death and Toll-like Receptor 9 Agonism to Generate Abscopal Effects in Canine Osteosarcoma. Timothy M Fan DVM, PhD. University of Illinois
MAF Grant D15CA-047: Understanding Why and How Canine Osteosarcoma Tumors Spread. Dr. Jaime F. Modiano, University of Minnesota
AKCCHF Grant #01806: A Novel Virus-Based Anti-Tumor Treatment for Canine Osteosarcoma. Bruce F Smith, VMD PhD, Auburn University.
AKCCHF grant #00778: Role of Regulatory T Cells in Dogs with Osteosarcoma. Barbara J Biller, DVM, Colorado State University
AKCCHF grant #00982: Evaluation of Efficacy of Fasaret in Dogs with Osteosarcoma. Don Bellgrau, PhD, ApopLogic Pharmaceuticals LLC
AKCCHF grant #01046-A: The Relevance of Ezrin in the Metastatic Progression of Canine Osteosarcoma. Sun Hyeok Hong, DVM PhD, National Cancer Institute