Medical Oncology: Canine Heart-Based Tumors

What Are Heart-Based Tumors?

The phrase “heart-based tumor” encompasses several types of cancer, including hemangiosarcoma, lymphoma, chemodectoma (also called aortic body tumors or paragangliomas), and ectopic thyroid tumors.

What Are The Clinical Signs?

The most common clinical signs associated with heart-based tumors are related to fluid building up around the heart (pericardial effusion.) Signs of pericardial effusion include weakness (difficulty rising, stumbling), collapse, loss of consciousness, cold limbs, pale gums, labored breathing, increased resting breathing rate, exercise intolerance, vomiting, or abdominal distension. Dogs with heart-based hemangiosarcoma can show collapse or even sudden death due to rupture of the primary tumor and fatal bleeding.

What Diagnostics Are Performed?

Diagnosing the specific type of heart-based cancer can only be achieved by obtaining samples of cells from the tumor (cytology or biopsy), which is usually perceived as highly challenging and risky. However, this should not preclude discussing performing procedures to obtain a definitive diagnosis, as it can be
successful.

A presumptive diagnosis is most often made by evaluating the location and appearance of the tumor with an echocardiogram (heart ultrasound). However, these predictions are only sometimes accurate.

What Are The Treatment Options?

Discussion of treatment options for heart-based tumors is challenging, given that we often do not have a specific diagnosis, and much of the conversation is theoretical regarding potential outcomes, risks, and benefits.

One option for dogs with small tumors, presumed to be chemodectomas, that do not cause clinical signs is careful monitoring. These tumors are usually slow-growing and may never cause clinical signs. For these patients, the safest approach is to have periodic heart ultrasounds (every 3-6 months) to track growth over time.

Surgery

Surgical options vary depending on the tumor type and location. Surgery is challenging because the tumor is often located near or within critical blood vessels, nerves, and the heart itself. Surgical options can be discussed during your appointment.

A palliative surgery, where a portion of the tissue surrounding the heart (pericardium) is removed, is a more realistic option for most dogs. This allows fluid or blood to drain into the chest cavity, preventing it from compressing the heart. This does not treat the tumor itself but can lessen clinical signs.

Radiation Therapy

Radiation therapy is usually performed as an alternative to surgery. There are several options for radiation therapy for heart-based tumors, including:

SRT: Stereotactic radiation therapy (also referred to as SRS, radiosurgery, or Cyberknife-type therapy) involves precise delivery of focused radiation beams to the tumor while shielding surrounding organs. It is usually given in 3 treatment sessions on back-to-back days. Dogs with a lot of fluid build-up in or around the lungs or surrounding the heart are not good candidates for this treatment option.

Full-course radiation therapy: When SRT isn’t possible, full-course radiation may be an option. This is given once a day (Monday through Friday) for four weeks (20 treatments total). Each of these treatments is provided under general anesthesia.

The cost for both forms of radiation is similar. The cost varies between patients and may be higher if additional tests are recommended. The total price is usually between $9,000 and $12,000.

RT FOR CHEMODECTOMAS

Chemodectoma tumors shrink rapidly with SRT, often by 50% or more within the first 3-4 months after treatment. In our radiation oncologist’s experience, the tumor’s growth is controlled for an average of about 12-18 months before it starts growing again. At that point, additional radiation therapy could be considered. Full-course radiation therapy causes most chemodectomas to shrink more slowly than SRT.

RT FOR CARDIAC HEMANGIOSARCOMA

Radiation therapy can reduce the size of hemangiosarcoma tumors and decrease bleeding. We currently recommend a protocol that involves two treatment sessions (on back-to-back days). The cost is currently estimated to be between $3,000 and $4,000.

Chemotherapy

Chemotherapy can be used to treat heart-based tumors. The goal of chemotherapy is to slow down the spread of cancer to other parts of the body. Chemotherapy can be combined with RT for better tumor control.

CHEMOTHERAPY FOR CHEMODECTOMAS

We use a drug called Palladia (toceranib phosphate) to treat chemodectomas in dogs. This is an oral medication given at home. Most dogs with chemodectomas that receive Palladia have temporary improvement or even resolution of their clinical signs.

CHEMOTHERAPY FOR CARDIAC HEMANGIOSARCOMA

Doxorubicin is the drug of choice for treating cardiac hemangiosarcoma. This is an intravenous injection given every 2-3 weeks. When chemotherapy is combined with radiation therapy, we may start treatment with a different intravenous drug called carboplatin. The first dose of carboplatin is given a few hours before the dose of radiation therapy.

Drug	How Is It Given?	How Often Is It Given?	Approximate Cost*
Doxorubicin	Intravenously	Every 2-3 weeks for 6 treatments total	$500-$600 per treatment
Carboplatin (used in dogs receiving radiation therapy)	Intravenously	Every 3 weeks for 4 treatments	$500-$600 per treatment
Palladia	Orally (at home)	Every other day or three times per week	Varies based on body weight

Getting Started

Once you have determined the best option, we will work with you to develop an appointment plan. Appointments for patients undergoing treatments and rechecks must be scheduled in advance. All recheck appointments are drop-off appointments.

Drop-offs are between 7:30 am-8:30 am.
Pick-ups occur by 6:00 pm.
No discharges occur between 2:30-3:30 pm as our oncology team is in rounds.
*Costs are estimates. The overall cost depends on patient response. Estimates do not include supportive care or hospitalization