The Diagnosis No Large Breed Dog Owner Wants to Receive

Analysis by Dr. Karen Shaw Becker

osteosarcoma

Story at-a-glance -

  • Osteosarcoma is a very aggressive bone cancer that accounts for about 85% of all bone tumors in dogs, especially large and giant breeds
  • Early symptoms can include swelling, intermittent lameness and fractures; as the cancer progresses, pain and lameness rapidly escalate
  • The prognosis for canine osteosarcoma is generally poor, and conventional treatment options (surgery and chemotherapy) typically don’t significantly extend patients’ lives
  • Alternative treatment options include targeted nutritional therapy, including a ketogenic diet, and vitamin and herb protocols
  • Two different types of therapeutic vaccines to treat osteosarcoma are currently being studied, and both show promising results

Osteosarcoma is a very aggressive bone cancer that tends to spread rapidly (metastasizes) to other parts of the body. The disease is rare in cats, but sadly, it is diagnosed in an estimated 10,000 dogs each year in the U.S., and accounts for about 85% of all canine bone tumors.1

Symptoms of Bone Cancer

Many of the early signs of osteosarcoma are subtle and can include swelling, intermittent lameness, and joint or bone pain. Sometimes there is also lethargy and loss of appetite. Because a bone with a cancerous tumor isn't as strong as a normal bone, even a minor injury can cause a pathologic fracture of the weakened bone.

If the tumor affects a body part other than a limb, symptoms will depend on the location. For example, if the cancer is in the jawbone, the animal will have difficulty opening her mouth or eating. In cats, the nasal bones are occasionally affected by this type of tumor, which can cause nasal discharge and breathing problems.

As the disease progresses, it becomes more painful as the tumor grows and the bone is destroyed. Intermittent lameness will become more frequent until it's constant, typically within 1 to 3 months of onset.

Dogs at Highest Risk for Osteosarcoma and Additional Risk Factors

Dogs over 90 pounds account for almost one-third of cases of canine osteosarcoma, and the median age at diagnosis is about 8 years. In large and giant breeds, most tumors occur in the limbs. Breeds at the highest risk include the Saint Bernard, Great Dane, Irish Setter, Doberman Pinscher, Rottweiler, German Shepherd and Golden Retriever.

Dogs under 30 pounds account for less than 5% of osteosarcoma cases. In these dogs, the cancer typically affects the bones of the skull, vertebral column, ribs and sternum. Factors that can increase risk of bone cancer in dogs include:

Diagnosis and Staging

The primary diagnostic tests for osteosarcoma are X-rays and histopathology (examination of tissue). On an X-ray, osteosarcoma has a characteristic lytic or "moth-eaten" appearance. A fine-needle aspirate or bone biopsy of suspicious areas must be performed to confirm the diagnosis. Since many kitties become more lame and painful after a bone biopsy, it's preferred when possible to do a fine-needle aspirate instead.

Blood tests and chest X-rays are usually performed as well, to look for additional lesions and underlying medical conditions. Since up to 90% of osteosarcoma tumors have spread to the lungs by the time the disease is diagnosed, computed tomography (CT) scans and magnetic resonance imaging (MRI) are also often used to better assess lung involvement and to evaluate a pet's overall condition in more detail.

The disease will also be categorized as stage I (low-grade tumors without evidence of metastasis), stage II (high-grade tumors without metastasis), or stage III (metastasis has occurred).

Conventional Treatment of Osteosarcoma

Unfortunately, many pets diagnosed with osteosarcoma have a poor prognosis. Treatment is aimed at relieving pain and extending the animal's quantity and quality of life for as long as possible.

Depending on the situation, traditional treatment options are surgery, which may or may not involve amputation of the affected limb, and chemotherapy for animals that undergo amputation. Radiation therapy, which is used strictly as a palliative treatment to relieve bone pain and discomfort, may also be prescribed along with pain medications.

Sadly, pet parents often must make what is known as the "leg or life decision" for their pet. Survival times of about one year are achieved in 50% of dogs with osteosarcoma that undergo amputation of the affected limb, followed by chemotherapy. However, some dogs have actually survived five to six years after diagnosis.

Chemo is only given in cases where the primary tumor has been surgically removed and is wholly ineffective in animals who aren't candidates for surgery. I never advocate chemotherapy for these patients, as I have not seen it dramatically improve lifespan. Many owners of dogs diagnosed with osteosarcoma choose not to pursue amputation and focus instead on giving their pets the best quality of life for the time they have left.

Alternative Treatment Options and Immunotherapy Studies Underway

I follow veterinarian and naturopathic physician Dr. Steve Marsden's protocol for my patients whose guardians choose not to pursue surgery. His protocol involves using the injectable form of vitamins A and D, bromelain, omega-3 fatty acids and a blend of herbs called the Hoxsey Formula with boneset. I have also found using Chinese herbs in conjunction with Dr. Marsden's protocol to be beneficial.

I also recommend targeted nutritional therapy, which includes a ketogenic diet, for cancer patients. Some excellent resources for this approach include Dr. Ian Billinghurst's book, Pointing the Bone at Cancer, the KetoPet Sanctuary and Rodney Habib's The Dog Cancer Series.

There are at least two types of immunotherapy treatments for canine osteosarcoma currently under study. Both are therapeutic vaccines, not to be confused with preventive vaccines. One is a protein-tagged cancer vaccine designed to incite the immune system that is given instead of chemotherapy.

The other is a bacteria-based vaccine that recently received a conditional license by the USDA, which was granted based on the vaccine's effectiveness in a pilot study of 18 dogs. This vaccine is intended for dogs who have been diagnosed with osteosarcoma that expresses the Her2/neu target — a protein that is also commonly associated with breast cancer cells in women.

This target is expressed in about 40% of canine osteosarcomas. The theory behind the vaccine, which contains a genetically modified bacteria, Listeria, that expresses the Her2/neu marker, is that it will stimulate the immune system to kill the bacteria and also the cells that express Her2/neu.

The vaccine is delivered intravenously after tumor removal and chemotherapy, and the median survival rate in the pilot study dogs was 956 days, compared with 423 days in a historical control group.

According to Dr. Nicola Mason of the University of Pennsylvania School of Veterinary Medicine, who helped develop the vaccine and the pilot study, if the vaccine is able to effectively stimulate the immune system, then immune cells will find and destroy any remaining cancer cells that have survived chemotherapy. It is also intended that the immune system will be left with a memory of the cancer cells and will be able to inhibit development of further osteosarcoma lesions.

Of course, as regular visitors here at Mercola Healthy Pets know, my general opinion of vaccines is that they should be used with extreme caution and only when truly necessary to protect a vulnerable animal from a specific disease. In fact, many of you have an automatic negative response to even the mention of the word "vaccine."

However, most of the adverse reactions and side effects associated with vaccines are the result of the toxic adjuvants they contain. Even though the products described above are called vaccines, they're really closer to an unadjuvanted form of immunotherapy. They are newly developed products being studied for their ability to treat an aggressive, life-ending cancer, and I'm not opposed to non-toxic immunotherapy.