Osteosarcoma In Cats

What Is Osteosarcoma in Cats?

Osteosarcoma (OSA) is an aggressive or malignant bone cancer that affects any part of the skeleton. In cats, appendicular OSA may affect the limbs, pelvis, shoulders, or paws. It is much more common than axial OSA, which may target the head, neck, or spine. Appendicular OSA affects the pelvis more often than the forelimbs, and the jaw is the most common bone affected by axial OSA.

Often arising from the bone itself, the cancer starts to eat away at the bone, causing pain, inflammation, and eventually a fracture. Over time, the cancer may spread to the lymph nodes, chest, spleen, and other areas of the body.

Bone cancer is not as aggressive in cats as it is in dogs, and it and metastasizes only 5-10% of the time. OSA affects male and female cats of any age, and even though this type of cancer is rare, older cats are more apt to get it.

Symptoms of Osteosarcoma in Cats

One of the first signs of OSA in cats may be a change in behavior or the development of lameness.  Bone cancer in cats is extremely painful. Your cat may stop eating and may be withdrawn, more irritable, and aggressive. 

The symptoms of OSA are often related to where the tumor originated. For example, if your cat’s tumor affects one of their limbs, you may notice lameness, swelling, and pain to the touch at the site as well as a reluctance to walk, run, or jump.

If the tumor affects the cat’s jaw, then you may notice your cat having difficulty eating, swallowing, or opening and closing the mouth, and they may lose weight as a result.

As the bone cancer progresses, fractures can occur. You may notice an acute start of lameness, disuse of the limb, misalignment of the jaw, and a refusal to walk altogether. If you notice any signs of a broken bone, your cat should be examined by your veterinarian immediately.

Causes of Osteosarcoma in Cats

Cancer occurs often and for reasons that are not well understood. Multiple factors such as age, UV damage or other environmental triggers, DNA mutations, and genetics have been associated with certain cancers. Rarely is there a single cause for cancer; the development of bone cancer is no different.

How Veterinarians Diagnose Osteosarcoma in Cats

To diagnose bone cancer in your cat, your veterinarian will perform the following:

• Physical exam to find the affected location 

• X-ray of affected area

• Chest CT scan and abdominal ultrasound to look for metastasis 

• Cytology (fine-needle aspiration of mass)

• Biopsy (large needle is inserted into the lesion to obtain a core of bone) 

Once diagnosed, your veterinarian will determine how far the bone cancer has spread, which can include a cytology of the lymph nodes, abdominal ultrasound, and chest x-rays, if not already taken.

There are other more advanced diagnostics, such as CT or nuclear scintigraphy, that might be needed and that are usually done at a referral facility. 

Treatment of Osteosarcoma in Cats

First, pain should be appropriately managed in all cases of feline OSA. Your veterinarian will often prescribe pain medications such as buprenorphine, gabapentin, amantadine, or NSAIDs such as robenacoxib or meloxicam. 

Another form of controlling pain is amputation of the affected limb. Amputation alone may also cure those cats affected by appendicular OSA. For cats with axial OSA, mandibulectomy or maxillectomy (removal of part of the jaw) surgery is most often performed. 

Chemotherapy, radiation, and surgery are all treatment options for bone cancer in cats. Radiation, though uncommon, may help improve patient comfort and decrease inflammation. Chemotherapy is used if surgery is not an option. 

Regardless of treatment type, most cats have an average survival rate of 12 months for appendicular OSA and six months for axial OSA. However, for cats that have had an amputation, the average survival rate was about four years. 

Cats with evidence of metastasis or cancer of the humerus (forelimb bone) often have a poorer prognosis. Consultation with a veterinary oncologist to discuss your cat’s treatment and prognosis is recommended.

Recovery and Management of Osteosarcoma in Cats

Adequate pain control is important throughout your cat’s treatment. Follow your veterinarian’s guidelines and recommendations and adhere to follow-up appointments. 

Cats undergoing radiation or chemotherapy may need special care, such as their pet parents learning how to deal with their waste or administering long-term medications. Follow-up appointments and future screenings are vital to check for signs of cancer recurrence. 

For cats that have had an amputation, your vet will prescribe four weeks of cage rest for recovery. Keep in mind that cats often do remarkably well on three legs and rarely are hampered by their missing limb. Don’t neglect to consider amputation as a viable solution.