Osteosarcoma

Patty Khuly

Summary

Osteosarcomas are highly aggressive tumors that occur as a result of the abnormal proliferation of osteocytes, the cells that make up bone. As such, these painful tumors arise from anywhere in the skeleton, though usually in the limbs.

In dogs, osteosarcoma tumors are considered the most common cancer of the bone. Though they are considered locally aggressive because they destroy existing bone while making abnormal new bone, these tumors are also notorious metastasizers, which means they spread readily to distant, non-bony sites in the body.

As large and giant breeds of dogs are overrepresented and certain breeds predisposed, a genetic origin for this disease has been inferred. The exact method of inheritance, however, is unknown. As with so many other cancers, it’s impossible to pinpoint the exact cause of osteosarcoma. A combination of genetic and environmental factors is assumed.

Unfortunately, without treatment, the prognosis for all osteosarcoma patients is grave. Unless treated aggressively and early, these tumors will invariably result in an orthopedically painful death. However, even with aggressive treatment (surgery and chemotherapy, with or without radiation), survival times average only ten to twelve months.

Symptoms and Identification

Osteosarcoma tumors almost always present as lameness. Afflicted dogs will suddenly start limping on one limb alone. Moreover, they will be very painful to the touch over the affected area. The following tests are strongly recommended in the course of initial diagnosis:

  • Physical examination
  • X-rays
  • Complete blood count (CBC)
  • Blood biochemistry panel
  • Urinalysis
  • Chest X-rays to
  • Fine needle aspirate of nearby lymph nodes

Fine-needle aspiration of the lymph nodes, though useful in determining the extent of the disease, offers only partial information. Like so many other cancers, the disease can only be diagnosed definitively by retrieving a specimen from the affected tissues (biopsy) and evaluating it through histopathology (microscopic analysis of the tissues by a board-certified pathologist). In the case of osteosarcoma, this is always achieved via bone biopsy.

A bone biopsy is an anesthetic procedure in which an instrument is inserted into the bone to retrieve a bit of the bony tissue for histopathological examination.

If treatment is to be considered, chest X-rays and fine needle aspiration of the lymph nodes are especially essential. These tests help determine the extent of the disease’s progression and helps outline a patient’s individualized treatment plan.

Affected Breeds

Osteosarcoma can affect any breed of dog but large and giant breeds are overrepresented among its sufferers. Among these, Irish Wolfhounds, Rottweilers, Greyhounds, Great Danes, Irish Setters, and Samoyeds are most at risk.

Treatment

Because osteosarcoma tumors affect the limbs most often, the most common approach to treatment requires amputation. Though this aggressive approach is almost always emotionally taxing for owners, dogs will almost uniformly feel tremendous relief once the limb and its excruciatingly painful tumor are removed.

Because a percentage of these patients may be candidates for complex limb-sparing surgical techniques, and because amputations can be fraught with complications, board-certified surgeons are strongly recommended for these patients. Once surgery is complete, or in cases where surgery is not possible, incompletely effective, or not elected, chemotherapy, radiation, and/or advanced cancer vaccine technology may be utilized to help keep tumors from metastasizing, eliciting severe pain, or progressing as quickly as they might otherwise.

It is strongly recommended that owners who hope to gain most comfortable longevity on behalf of their pets consult a board-certified oncologist to receive the fullest understanding of the broad range of their pet’s treatment options.

After surgery, chemotherapy is by far the most common approach to osteosarcoma treatment. Because it helps delay the spread of this disease to distant sites (metastasis), it typically extends a dog’s life from four to six months (with surgery alone) to ten to twelve months.

Should surgery not be an option (for whatever reason), palliative radiation therapy may be elected. This approach consists of two consecutive twice-daily doses of radiation therapy. The goal is to alleviate pain and swelling caused by the tumor.

Because over seventy percent of patients with osteosarcoma benefit from palliative radiation therapy for approximately 2-4 months post treatment, it’s strongly recommended when surgery is not performed.

Veterinary Cost

As with many cancers that require surgery and an oncologist’s advice for best effects, the cost of this disease can be impressive and prohibitive. Pets who suffer from these tumors may experience treatment costs that extend well beyond the $10,000 mark. That is, if owners elect to enlist all possible approaches to treatment.

Because it involves a specialized anesthetic procedure, the cost of definitive diagnosis is typically around $800 to $1,000. However, if owners know they are unwilling to pursue targeted treatment of any severe bony disease, the cost is significantly lower. This is because almost all bone lesions are easily diagnosed via simple X-rays of the affected area ($500 or less).

The cost of surgery itself will depend on the surgeon’s degree of specialization along with the anatomical location of the tumor, but $1,000 to $3,000 is typical. Chemotherapy will typically add another $2,000 to $4,000 (depending on the protocol elected and the patient’s size). Palliative radiation tends to cost anywhere between $2,000 and $5,000.

It cannot be overstated that the cost of diagnosis and treatment depends on many factors including geographic location (cost of living), standard of care (lower vs. higher standards of veterinary care), whether specialty hospitals are employed (higher quality equipment, certified personnel, and board-certification for veterinarians specialized in the fields of surgery and oncology).

Unfortunately, many owners elect not to treat their pets due to the fundamentally grave prognosis and the extreme expenses associated with this disease.

Prevention

As with most cancers of genetic and indeterminate origin, there is no accepted approach to the prevention of osteosarcoma.



References

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Bergman PJ, MacEwen EG, Kurzman ID, et al. Amputation and carboplatin for treatment of dogs with osteosarcoma: 48 cases (1991-1993). J Vet Intern Med 1996;10:76-81.

Kent MS, Strom A, London CA, et al. Alternating carboplatin and doxorubicin as adjunctive chemotherapy to amputation or limb-sparing surgery in the treatment of appendicular osteosarcoma in dogs. J Vet Intern Med 2004;18:540-544.

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