What You Should Know About Osteosarcoma (Bone Cancer) In Cats

Playful calico cat with orange eyes and laying on her back ready to play

A type of bone cancer called osteosarcoma is the most common type of primary bone cancer, accounting for over 95% of all bone tumors. Other types of bone cancer are chondrosarcoma, fibrosarcoma, and hemangiosarcoma. “Primary” refers to cancer that starts in the bone versus spreading (metastasizing) into the bone from somewhere else.The cause of osteosarcoma in cats isn’t well understood.

Does My Cat Have Osteosarcoma?

Osteosarcoma can occur in any bone in a pet’s body. Osteosarcoma is extremely aggressive, and it spreads quickly to other parts of the body, making early detection and treatment vital. While osteosarcoma is also the most common type of bone tumor in cats, it’s relatively uncommon overall. In addition, osteosarcoma is much less aggressive in cats than in dogs.

Signs and Symptoms of Osteosarcoma in Cats

The symptoms of osteosarcoma in cats can be subtle, and they may include:

  • Lameness that doesn’t go away and swelling of the affected bone; these are the most common symptoms when a tumor affects a limb
  • Swelling or a mass; this is often the first sign of a tumor in the skull, jaw, or ribs
  • Difficulty eating if a tumor affects the jaw
  • Neurologic signs, such as seizures or a wobbly gait, with the skull or spinal/vertebral tumors
  • Breathing difficulties or lameness with rib tumors
  • Loss of appetite and lethargy

Diagnosis and Staging Osteosarcoma in Cats

To diagnose osteosarcoma, veterinarians typically follow these steps:

  • First, your vet will take an X-ray and perform a physical and orthopedic examination to rule out other causes of lameness.
  • To obtain a definitive diagnosis and determine the best treatment plan for your pet, any problem areas identified on the X-ray will be biopsied.
  • Chest X-rays or a computed tomography (CT) scan, blood tests, and a urinalysis will be performed to assess your pet’s overall health and determine if cancer has spread (in 90–95% of dogs, the tumor will have already metastasized at the time of diagnosis; osteosarcoma most commonly spreads to the lungs).

Advanced CT imaging is often recommended for osteosarcoma tumors of the limbs because it provides better information for a veterinary surgeon to determine if surgery is possible and the extent of surgery necessary to achieve a favorable outcome.

Treatment Options for Osteosarcoma in Cats

Because osteosarcomas tumors are so aggressive, amputating the affected limb followed by chemotherapy to treat metastasis is the most common treatment. While amputation isn’t the right option for all pets, otherwise healthy cats can function quite well with three legs. Limb-sparing surgery—in which the tumor is removed and the bone is replaced with another bone (either from your pet or from a bone bank)—may be an option depending on the tumor’s location and whether it is relatively small at the time of diagnosis. The complication rate for this type of surgery, particularly infection, is relatively high, however. When surgery isn’t an option due to tumor location, stereotactic radiation (SRS/SRT) can be beneficial. It can also be an alternative to amputation for cats in which the osteosarcoma hasn’t destroyed a great deal of bone. This advanced, highly accurate type of radiation therapy focuses high doses of radiation to damage and kill osteosarcoma cells. Follow-up chemotherapy is still necessary. The main advantage of SRS/SRT is that it delivers high doses of radiation with sub-millimeter precision. This means:

  • Maximum damage to the tumor and minimal collateral damage to healthy tissues nearby
  • Fewer treatment sessions compared to conventionally fractionated radiation therapy (CFRT)—patients require only 1-3 sessions, which means fewer anesthetic events, less risk, and less disruption to your schedule
  • Potential for quicker recovery with fewer side effects
  • Ability to treat tumors previously considered untreatable with radiation
  • PetCure Oncology’s radiation oncologists are experienced using SRS/SRT to treat cats with osteosarcoma

Palliative treatment, which aims to make your pet more comfortable but doesn’t provide a cure, can include conventional radiation therapy and drugs to reduce pain.

Osteosarcoma in Cats: Life Expectancy, Survival, and Prognosis

The prognosis for pets with osteosarcoma depends on the severity and spread of the disease and on the treatment you choose. As with any cancer, the earlier it is diagnosed and treated, the better the chances that treatment will be successful.

Meet Our Osteosarcoma Pet Heroes

Here are a few our inspiring Pet Heroes that have fought bone cancer. We invite you to read their stories. If your pet was diagnosed with osteosarcoma, contact our Pet Advocates at (833) PET-HERO. Our team members are ready to help answer your questions.

“Bone tumors in cats and dogs,” acvs.org
“Osteosarcoma in dogs and cats,” petcarerx.com
Types of Cancers In Cats

If your pet is displaying any symptoms of cancer or has been diagnosed with cancer, sort below by cancer type or tumor location to learn more about each cancer type and available treatment options for your pet. Click on the links for more specific information on treatment and real patient stories.




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