Cancer of the heart and associated structure is uncommon. They occur most commonly in middle aged to older dogs. The most common cardiac tumors include hemangiosarcoma and heart-based masses or chemodectomas. Other less common tumors include lymphoma, sarcomas, and ectopic thyroid tumors. The symptoms of cardiac tumors are often related to altered cardiovascular function due to pericardial effusion, cardiac tamponade, compression of the heart, disrupted contractility or rhythm, and/or right sided heart failure. Diagnosis of a cardiac tumor is usually made off of history, physical exam, location of the mass, breed of dog, and radiographic and echocardiographic findings. Cardiac troponin levels may be useful in supporting the diagnosis. Aspiration and cytology of the mass directly is not often performed. Pericardial fluid analysis may be evaluated but is often not diagnostic for a specific tumor type. pH has been used to differentiated idiopathic pericardial effusion from neoplasia.

Hemangiosarcoma

Hemangiosarcoma is the most common cardiac tumor. Breeds at risk for cardiac hemangiosarcoma include German Shepherds and Golden Retrievers, and spayed females are at increased risk compared to intact females. They most commonly occur on the right atrium but have also been reported to occur in the right ventricular free wall, intraventricular septum, and main pulmonary artery.

Chemodectoma

Brachycephalic breeds, especially Boxers, Bulldogs, and Boston terriers are at increased risk for developing chemodectomas.  Female spayed dogs have a higher risk for developing achemodectoma compared to intact females.  Chemoreceptor cells monitor oxygen and carbon dioxide levels in the blood, and regular heart and respiratory rate.  They reside in the aortic body, carotid body/bifurcation, and other locations in the body. Aortic body tumors often caused right sided congestive heart failure.

Treatment options for cardiac tumors include:

Local therapies to address the risk of recurrent cardiac tamponade

Surgery:  Surgery is not often possible unless the tumor involves the right auricular appendage.  Another option is pericardiectomy or pericardial window which may help to alleviate symptoms related to cardiac tamponade. This may be performed via thoracoscopy which is less invasive with decreased operative time and complications.  Prognosis following pericardectomy for an aortic body tumor has been reported approximately 2 years compared to <2 months without.

Radiation therapy:  Sporadic case reports of radiation therapy would suggest a benefit from radiation therapy in the treatment of cardiac tumors in dogs.  A small study evaluating the use of radiation therapy for cardiac hemangiosarcoma. The results reduced frequency of pericardial effusion necessitating pericardiocentesis and may provide a clinical benefit.  Chemodectomas are thought to be radiation responsive tumors.  Gradual regression is often seen after treatment with a reasonable expectation for obtaining a durable response of > 1 year. 

Chemotherapy: The most common chemotherapy recommendation for cardiac hemangiosarcoma is doxorubicin. Treatments are administered as IV infusions every 2-3 weeks for 5 treatments.  In the setting of gross disease, the likelihood of benefit with doxorubicin is typically considered to be ~25%, although a single study reports a 60-70% chance of a biologic response (CR, PR, SD).  Dogs that do not respond to chemotherapy will often show significant progression within a month.  In dogs who do respond, response and survival times are generally 4-6 months, although rare longer-term responses have been reported.  Serial cardiac ultrasounds can be used to monitor for disease progression and assess response to therapy. 

Palladia is the most common recommendation for treating chemodecomtas.  Palladia is a receptor tyrosine kinase inhibitor that is administered orally every other day or three times/week at home, which targets mutated growth receptors.  Several small studies have shown a possible clinical benefit to treating dogs with non-resectable chemodectoma with Palladia.  A small retrospective study showed that between 10-30% of dogs have a response to Palladia regardless of if metastasis is present.  The reported survival times were 523 days and 796 days, with and without metastasis respectively. In addition, many oncologists have reported complete remission and survival of 1-2+ years when treating heart-based masses such as chemodectomas.  Palladia would be the preferred option for a chemodectoma or heart based mass.

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 About the Author: Stacy Santoro Binstock, DVM, DACVIM (Oncology)

Dr. Stacy Binstock is a NJ native who was transplanted to the midwest for 7 years for vet school and residency training. She has been working as a medical oncologist in private practice for over 15 years. Her passion is to provide personalized, practical options for treating cancer in pets, and to give her clients and patients an excellent experience despite the difficult journey. Stacy created an oncology telemedicine service called Lotus Pet Oncology to provide access to cancer care for dogs and cats nationwide.