Bone Cancer (Osteosarcoma) in Dogs

Key Takeaways

Osteosarcoma is the formation of a malignant tumor in the bones. It is a highly metastatic cancer with a median survival rate of 2-4 months without treatment and 8-12 months with treatment. 

• This is the most common type of bone cancer in dogs and is most prominent in large breeds and older pets

• The symptoms of osteosarcoma include lameness, bone pain, swelling, limb asymmetry, and fragile bones (breaking with minimal trauma)

• Diagnostics include x rays, bone scans, biopsies, urinalysis, and blood work

• Treatment involves surgical removal of the tumor, generally through amputation where possible, and chemotherapy

• Radiation as well as anti inflammatories and pain management are palliative care options

• Prognosis is very poor and treatments are often used to minimize pain and improve comfort for the dog

A Closer Look: What is Osteosarcoma in Dogs?

Osteosarcoma primarily is found in the limbs but can rarely affect bones in the skull, pelvis, or spine. Secondary symptoms seen in cases of osteosarcoma include

• Limb swelling

Difficulty breathing

Coughing

• Loss of appetite

The prognosis for osteosarcoma is very poor. Even with treatment, the median survival time is under one year. Without treatment, survival time is between two and four months.

Risk Factors

Osteosarcoma is not the only type of cancer to affect the bones.  Secondary tumors (metastasis) may form in the bones/marrow, and other types of primary bone cancers include:

• Chondrosarcoma 

• Fibrosarcoma

Lymphoma

• Hemangiosarcoma 

Bone cancer is more common in large breeds (50+ pounds) and is in dogs between 18-24 months of age and dogs over the age of 7. It is most commonly diagnosed in dogs between the ages of 6-8. Strong breed predispositions suggest a genetic component. 

In rottweilers, spaying or neutering at an early age may contribute to a predisposition. 

Prior radiation therapy for other cancers may predispose dogs to developing osteosarcoma.

Possible Causes

The cause of osteosarcoma is mostly unknown. 

Osteosarcoma may develop at the site of previously healed fractures or infections (osteomyelitis).

Main Symptoms

The primary symptoms of osteosarcoma include

• Lameness

• Bone pain

• Fragile bones

• Limb asymmetry/mass around the limb

Testing and Diagnosis

After a physical examination and medical history, a number of tests can confirm osteosarcoma:

• Diagnostic imaging (x ray, ultrasound)

• Biopsy

• Blood analysis

• Urinalysis

• Bone scan

Steps to Recovery

Once osteosarcoma is confirmed, treatment can involve a number of options. In cases of osteosarcoma in a limb, amputation is often the first course of treatment, but limb-sparing options are also available. Chemotherapy is often performed in conjunction with surgery. Radiation is used as a method to minimize pain and spread of the tumor. Other methods including pain treatment, activity modifications, and anti-inflammatories can be used to minimize symptoms.

Immunotherapy options are currently under investigation.

Osteosarcoma is highly metastatic and most often fatal. Treatment can extend the life expectancy (2-4 months without treatment vs. 8-12 months with) but most care is palliative and managing symptoms.

Prevention

The cause of osteosarcoma is not known and due to this, there is little that can be done to prevent its formation. It is recommended that any limb weakness or inflammation is addressed promptly by a vet so early cases of the sarcoma can be identified and treated rapidly. Osteosarcoma is not contagious.

Is Osteosarcoma Common in Dogs?

Osteosarcoma is the most common bone cancer in dogs.

Typical Treatment

• Surgery

• Chemotherapy

• Palliative care

• Radiation

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