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Dog: Osteosarcoma

General information

Other common/scientific names: bone cancer

Osteosarcoma is a common type of malignant bone cancer. It usually originates from the leg bones and tends to occur at the end of the bones near the growth plates. Older large and giant breeds are more commonly affected including Labrador Retrievers, Rottweilers, Doberman Pinschers, Newfoundlands and Saint Bernards. Up to 90% of osteosarcomas will metastasize or spread to the lungs.

Causes

It is unknown what causes osteosarcoma but one theory suggests that the rapidly growing cells found in the growth plates of large breed dogs are more apt to undergo mutation. Trauma or chronic stress on a bone is also thought to play a part in the development of cancerous cells.

Cardinal symptom

Lameness

Symptoms

Osteosarcoma is an aggressive type of bone cancer which develops deep within the bone, destroying bone as it grows outward. This results in pain that becomes progressively worse causing l ameness and reluctance to move. As the tumor grows, the bone will develop a pronounced, painful swelling. Pathological fractures may occur. These are fractures which result because the bone is weakened from the cancer. Poor appetite, weight loss and lethargy are signs of advancing cancer.

Diagnosis

Radiographs of the affected limb are needed to diagnose bone cancer. While the appearance of the bone on a radiograph is suggestive of osteosarcoma, a biopsy of the tumor is needed for a definitive diagnosis. Bone infection (osteomyelitis) and other types of cancer can mimic the appearance of osteosarcoma. A complete blood count (CBC), serum biochemistry profile and urinalysis are recommended to assess organ function. A radiograph of the chest is performed to check for spread of the cancer. A bone scan can be performed to determine if multiple bones are affected. This procedure is only available at specialty clinic or universities.

Treatment

The goal of treating osteosarcoma is to control the pain and fight the spread of the cancer. Dog owners should be encouraged to consult with a veterinary oncologist when diagnosed with osteosarcoma.

Surgical removal of the tumor with limb amputation is most commonly recommended. This provides immediate relief from the pain. However, it is only palliative (pain relieving). Survival is not enhanced by amputation. Chemotherapy done in conjunction with amputation is usually prescribed after surgery to prolong survival time. For the most part, dogs tolerate chemotherapy well. Radiation therapy is used to kill cancerous cells and help with pain relief in dogs that are not good candidates for surgery. Radiation seldom prolongs survival time. Limb-sparing surgery is being performed at a limited number of veterinary specialty practices. This technique involves removing the cancerous bone and replacing it with either a bone graft or the remaining bone is re-grown using a new technique called bone transport osteogenesis. It is most useful for giant-breed dogs whose ability to walk after amputation may be questionable.

There are numerous analgesic (pain relieving) medications available to dogs with bone cancer if limb amputation and radiation therapy is not pursued. These include NSAIDs (non-steroidal anti-inflammatory drugs), bisphosphonates, narcotics and miscellaneous supplemental pain relievers. Many times, a combination of medications is needed to control pain.

Prognosis

Osteosarcoma is a fast spreading, life-threatening cancer. Survival time for dogs without chemotherapy is 4 to 5 months. Life expectancy with chemotherapy can be 10-12 months.

Prevention

Osteosarcoma is not preventable. And, even though a heritable link has not been discovered, any dog with a history of bone cancer is its pedigree should not be used for breeding.

Tips

Many owners are reluctant have their dog undergo a limb amputation. Keep in mind that dogs can return to almost normal levels of activity with one leg missing. Also, dogs do not suffer from the stigma of having a limb removed. Limb amputation offers an excellent method for pain resolution.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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