Hemangiosarcoma – A Heartbreaking Cancer That Strikes Without Warning

Updated June 15, 2021 – Hemangiosarcoma is a common and deadly cancer of dogs. The cancer tends to grow and spread rapidly, rarely giving the owner any clue their dog is harboring a deadly disease – until it suddenly strikes.

Knowing more about how this cancer develops and learning to recognize the subtle signs of the disease is important for owners, not only to spot a potential problem, but also be prepared if hemangiosarcoma affects their dog.

Hemangiosarcoma arises in sites with a rich blood supply

Hemangiosarcomas begin with uncontrolled growth of the cells lining blood vessels. Because of their abundant blood supply, the heart and spleen are the two most common sites where this type of tumor is found. This predilection for growth in blood-rich areas is the reason these tumors are so deadly. Hemangiosarcomas can suddenly rupture, causing massive blood loss, and forcing owners and veterinarians to make difficult decisions within minutes of diagnosis.

Hemangiosarcoma is a disease of larger-breed, older dogs

Hemangiosarcoma most commonly affects:

• Middle-aged to older dogs
• German shepherds, golden retrievers, Portuguese water dogs and Labrador retrievers
• Slightly more males than females (in some studies)

Unfortunately, no clinical signs (symptoms) are classic for hemangiosarcoma other than sudden, profound, internal bleeding. Other clinical signs sometimes reported by owners include:

• Intermittent lethargy or fatigue
• Anorexia
• Panting
• Sudden collapse
• Sudden death

Most pet owners are quick to act in cases of sudden collapse and time is of the essence in cases of hemangiosarcoma. These are true medical emergencies and many patients require immediate surgery to remove the bleeding mass (if possible), followed by supportive care to survive.

Long-term survival statistics are bleak

Even when a tumor is quickly detected and removed, the outlook for dogs with hemangiosarcoma is grim. Statistics show that:

• Average survival time with surgery alone is one to three months
• Average survival time with surgery and chemotherapy is five to seven months
• 90% of dogs are deceased one year post-diagnosis despite surgery and chemotherapy with almost 100% mortality two years post-diagnosis

Survival times have remained static for nearly 30 years, and new treatments are desperately needed. This is where Morris Animal Foundation comes in.

New ideas and research on an old foe

Many current and past studies have been devoted to learning more about this terrible cancer. New findings reported in the last two years include:

• A recent study focused on small dogs with hemangiosarcoma found similar survival statistics as large-breed dogs with hemangiosarcoma
• Work continues on the effect of spay/neuter on the incidence of hemangiosarcoma, but no definitive conclusion has been reached yet
• Researchers from North Carolina State University found a higher incidence of the bacteria Bartonella spp. in some dogs with hemangiosarcoma and are doing more studies to clarify their findings

Results from the Golden Retriever Lifetime Study will be invaluable as we try to answer these important questions.

Golden Retriever Lifetime Study

Hemangiosarcoma is an important cancer of golden retrievers and is one of several cancers of special interest to the Foundation’s Golden Retriever Lifetime Study. We’re monitoring and collecting extra tissue and other biologic samples from all dogs in our cohort diagnosed with hemangiosarcoma.

In addition to samples collected at the time of diagnosis or death, we have banked samples on affected dogs dating back years that may point to risk factors associated with this cancer. Our hope is that researchers will be able to use these samples to develop early diagnostic tests as well as understand possible genetic links to this deadly disease.

The Golden Oldies project, which will compare DNA from older golden retrievers without cancer to DNA from Study dogs with cancer (including hemangiosarcoma), will provide additional, critically needed data on the underlying genetics of this cancer. Findings from this project could ultimately result in a diagnostic test to identify dogs at risk for this cancer.

Morris Animal Foundation is trying to improve the odds for dogs with hemangiosarcoma

Morris Animal Foundation has invested more than $3 million in over 20 years of research to improve the quality and duration of life for dogs diagnosed with hemangiosarcoma.

Our funded research has focused on:

• Disease basics – understanding the basic biology of hemangiosarcoma may open the way to new diagnostics, treatments and prevention
• Overcoming chemotherapy resistance – understanding why hemangiosarcoma becomes drug resistant could improve treatment success as well as identify new chemotherapy agents
• Genetic links – studying breeds commonly affected by hemangiosarcoma could lead to new diagnostic testing and clues to the role genetics play in the development of this disease

You can find more information in our new hemangiosarcoma white paper.

Morris Animal Foundation has been a leader in trying to find new, innovative therapies to treat hemangiosarcoma. We recognized that more work needed to be done on all aspects of hemangiosarcoma, from understanding the basic mechanisms of tumor spread to better treatments. Although we’re making steady progress, we’ve got a long way to go to unlock the secrets of this painful and deadly cancer. Learn more about ways you can help ensure that dogs live healthier, happier and longer lives!