Investigating a New Treatment for Hemangiosarcoma

Canine hemangiosarcoma is among the most challenging and mysterious diseases encountered in veterinary practice. It is an incurable tumor of cells that line blood vessels, called vascular endothelial cells. Hemangiosarcoma is relatively common in dogs; it is estimated that this type of cancer accounts for 5-7% of all tumors seen in dogs (300,000 – 420,000 cases/year). Considering the lifetime risk of cancer for dogs is between 1 in 2 and 1 in 3, we can calculate that 1.5 to 2.5 million of the ~72 million pet dogs in the United States today will get hemangiosarcoma and succumb from it. Although dogs of any age and breed are susceptible to hemangiosarcoma, it occurs more commonly in dogs beyond middle age (older than 6 years), and in breeds such as Golden Retrievers, German Shepherd Dogs, Portuguese Water Dogs, Bernese Mountain Dogs, Flat Coated Retrievers, Boxers and Skye Terriers. According to the Golden Retriever Health Study published in 2000, the estimated lifetime risk of hemangiosarcoma in this breed is 1 in 5, illustrating the magnitude of this problem.

Regrettably, the standard-of-care for this disease has not seen significant advancement over the past 20 or 30 years. The options for therapy of canine hemangiosarcoma are limited, largely because the disease is not diagnosed until the late stages. The standard consists of surgery to shrink or remove the primary tumor, when possible, followed by intensive chemotherapy. In some cases, surgery is not feasible, or it can be impractical or inappropriate (for example, if there is evidence of extensive metastatic spread to sites beyond the primary tumor). There is no other therapy that has been proven to be effective to manage or control hemangiosarcoma.

Several alternative and complementary approaches (diet, herbs, mystical energy, etc.) have recently become popular as people try to find treatments for canine hemangiosarcoma. This usually follows extensive publicity after a dog receives these treatments and survives longer than anticipated, leading proponents to advertise this as success and evidence that their approach is curative for hemangiosarcoma. The danger of attributing curative power to treatment approaches after an anecdotal response cannot be overstated. There is no reported case where one of these therapies has been consistently successful (or even as good as the standard of care) after it has been tested without bias to try to replicate the anecdotal response. In fact, sometimes such treatments can actually interfere with or increase the toxicity of chemotherapy drugs

There is presently no readily available, effective test for early diagnosis of hemangiosarcoma. Careful analysis of blood samples by experienced pathologists may hint at the presence of chronic hemorrhage and blood vessel abnormalities that are suggestive of hemangiosarcoma. However, this method is neither sensitive nor specific to confirm the diagnosis. Non-invasive imaging methods are useful aids to diagnose the disease. In particular, ultrasound is moderately specific, but it is not sensitive, and the tumor must be large enough to be grossly visible. In addition, biopsies are required for confirmation of imaging results.

The majority of dogs diagnosed with hemangiosarcoma die within 1 year of diagnosis, with a large proportion of dogs not surviving beyond 6–8 months. With respect to HSA involving the spleen, surgery alone has been associated with extremely short survival times.Median survival for dogs treated with surgery alone is approximately 90 days, and that is extended to approximately 180 days by the addition of chemotherapy using one of several protocols available. Because the goal for chemotherapy in pet dogs is to extend life with good quality, toxicity is generally not a major issue of concern, and when it occurs it is most often managed without much difficulty.