Oncology Update: Hemangiosarcoma

Oncology Update
Central Toronto Veterinary Referral Clinic
Kevin Finora DVM, Diplomate ACVIM (Oncology and Small Animal Internal Medicine)

Hemangiosarcoma (HSA) is a common soft tissue sarcoma of blood vessels. HSA is classically thought of as a tumour of the spleen. However, HSA is also found on the heart, liver and increasingly in the skin, subcutaneous tissues and muscle. Certain breeds have demonstrated a predisposition to HSA, including German Shepherds, Golden Retrievers and Labrador Retrievers. HSA has recently surpassed lymphoma as the most common cancer reported in North American Golden Retrievers. Cutaneous HSA occurs most commonly in dogs with minimal skin pigmentation or with thin hair coats, suggesting a UV exposure etiology. Interestingly, cutaneous HSA is much less aggressive and less metastatic, when compared to the visceral form. In cats, the incidence of cutaneous and visceral HSA is equal.

The Double Two Thirds Rule is an important rule of thumb to consider when splenic masses are noted in dogs. Two thirds of all masses on the spleen are malignant tumours and of these, two thirds are HSA. This means any given mass on a dog’s spleen has a 45% chance of being HSA. This tumour type is very aggressive with extensive metastatic involvement being common.

The work-up for suspected HSA should always include three view chest radiographs and abdominal ultrasound. HSA will be present on the heart in about 15-25% of cases, justifying an echocardiogram to assess for the presence of a right auricular mass. One reported problem with echocardiograms is that they have been demonstrated to be able to identify an auricular mass, if present, in 50% of cases. Some studies have questioned the utility of the routine use of this test. If an auricular mass is present, the recommendation would be to surgically remove the mass, as survival times for cardiac involvement are similar to those for splenic disease. For splenic HSA, low stage disease (non-ruptured mass, no metastatic lesions) has a better prognosis compared to higher stage disease. Obviously, complete excision is important for the best prognosis.

Therapy for hemangiosarcoma is multi-modal and includes the use of surgery, chemotherapy and anti-angiogenic therapy. When surgery alone is used, the average survival time is 19-86 days with 6% one-year survival. The aggressive and metastatic nature of HSA is the reason surgery is followed by chemotherapy. When surgery is followed with chemotherapy, the median survival time is 172 days.

Dog with HSA experience many associated conditions of concern, including a high incidence of thrombocytopenia (reported in 75-97% of cases), coagulopathies (noted in 50% of cases) and post-operative cardiac arrhythmias (24% of cases). It is for these reasons patients must be as stable as possible prior to surgery and will require intensive monitoring for the 24-48 hours following surgery.

Anti-angiogenic therapy is an additional adjunctive therapy used to treat HSA. Anti-angiogenic therapy is used because HSA is a tumour of blood vessels, ideal targets for anti-angiogenic therapy. Preliminary data suggest dogs treated with targeted anti-angiogenic therapy, following surgery and chemotherapy, appear to have an additional 3-9 month survival advantage beyond the 6-months noted for surgery and chemotherapy alone. It is for this reason anti-angiogenic therapy is included as a standard part of my treatment protocol for HSA.

Dr. Kevin Finora is a Board Certified Oncologist and Small Animal Internist who is part of the Healthcare Team at the Central Toronto Veterinary Referral Clinic. He is available for referrals and consultations Monday to Thursday (including Monday and Tuesday evenings). Please contact him with any oncology questions or concerns.

Emergency Veterinarian Toronto

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Categorised as: Oncology

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