Osteosarcoma and other bone cancers

What is bone cancer?

Cancer of the bones is seen in dogs, cats, humans, and other animals. Primary bone tumors are tumors that develop from cells that form the bone tissue. Tumors that originate in other tissues, or from cells that inhabit the bone marrow, also can spread to and invade bones.

Osteosarcoma, or cancer of the bone-forming osteoblasts, is the most common primary tumor of bone. Osteosarcomas are very common in dogs, but they are extremely rare in humans, and even more rare in cats. Read about other types of tumors that are seen in bone here.

Why does bone cancer happen?

The causes of bone cancer are only partially understood. About 15% percent of children that develop bone cancer come from families with known genetic predispositions to cancer. Large and giant dogs (generally dogs weighing more than 45 pounds) are at greater risk to develop bone cancer. It stands to reason, then, that this cancer is seen commonly in large breed dogs, including Great Danes, Rottweilers, Irish wolfhounds, greyhounds, Saint Bernards, and others. We can conclude from the best information available that both large body size (height and weight) and genetics contribute to risk. However, other factors (such as rapid growth and traumatic injuries to bone) can add to the risk of bone cancer in dogs and children. The genes responsible for the predisposition of certain dog breeds to develop bone cancer remain to be identified. Read more about why bone cancer happens here.

What are the signs of bone cancer in dogs?

Bone tumors cause destruction of bone, so pain and lameness in the affected limb are the most common signs. Sometimes there may be visible swelling in the affected area which may be painful to the touch. Because tumors damage normal bone, an affected bone may break easily and cause severe pain. Bone tumors can spread to the lungs, but breathing difficulty may not develop for many months.

How is bone cancer diagnosed in dogs?

The first step in diagnosis is a full physical exam with X-rays of the affected area. However, findings that are commonly seen on X-rays in pets with bone cancer can occasionally be seen in animals with other diseases. For example, there are several types of fungal and bacterial bone infections that can cause signs and X-ray results that resemble bone cancer. Therefore, additional tests are almost always required for a definitive diagnosis. Read more about how bone cancer is diagnosed in dogs here.

How can we tell if bone cancer has spread to other sites?

To create an informed treatment plan, it is important to determine whether the tumor is confined to the bone where the clinical signs were noted or if it has spread to other areas like the lungs or other bones. This is called “staging.” The standard tests for staging osteosarcoma include X-rays of the chest, basic laboratory testing (blood and urine tests), possible additional testing, such as fungal infection testing, and abdominal ultrasound. Advanced imaging procedures which are more sensitive than conventional X-rays, such as computed tomography (CT) scans, are being used more commonly to diagnose bone cancer. They are especially useful for bone tumors arising from the skull or ribs.

How can we prevent bone cancer in dogs?

No specific strategies have been shown to prevent bone cancer completely in dogs. Given the association of rapid growth and traumatic injuries with bone cancer risk, some relatively simple practices might reduce the overall risk of developing this disease. These include using diets formulated to control the growth rate of puppies from large breeds, and restricting certain types of exercise, like running on concrete or other hard surfaces until dogs reach physical maturity.

How is bone cancer treated in pets?

There are various options for treating bone cancer. Each patient might require a slightly different approach.

A combination of surgery and chemotherapy provides the best results for this disease in dogs. Surgery is the most important component of the treatment plan, as it removes the painful area and eliminates the risk of a pathologic fracture. Surgical removal of tumors in the legs is usually accomplished by amputation, and we find that dogs generally cope very well with the loss of a limb. Surgery is often all that is needed to treat bone tumors in cats.

Chemotherapy is recommended as part of the treatment for osteosarcoma in dogs because this cancer has a high rate of metastasis, even if there is not visible spread at the time of diagnosis. Chemotherapy is administered with the goal of extending life with excellent quality. It is important to remember that chemotherapy in animals often looks very different from chemotherapy in people. Veterinary oncologists do their best to maximize patients’ quality of life, and most patients proceed through chemotherapy without significant side effects.

There are several options which can improve comfort and quality of life for dogs with bone tumors that cannot be removed using surgery, such as radiation therapy, medications to help reduce bone breakdown, and oral pain medications. Prognosis for bone cancer patients is typically dependent on the underlying tumor type, so it is important to discuss these options with your oncologist.

Is the U of M doing any research into the causes and treatment of bone cancer?

Yes, the University of Minnesota is recognized as a world leader in bone cancer research. Our research is dedicated to further discover how genes and environment affect the development and survival of osteosarcoma, and to use these discoveries to develop new, more effective treatments for this disease. One breakthrough was establishing the existence of two distinct subtypes of osteosarcoma with different biological behavior, and showing that therapies using the immune system are likely to improve the outcome for some patients with osteosarcoma. Most recently, we have developed a blood test that might be useful for early detection of osteosarcoma in dogs at risk.

Are there any clinical trials for bone cancer in dogs at the U of M?

For the most up-to-date information on clinical trials, visit the Clinical Trials page.