FAQ about Hemangiosarcoma

I had never heard of hemangiosarcoma (HSA) before my dog was diagnosed. How common a cancer is it?

Taken as a tumor in general (including its counterpart seen in humans and in mice – angiosarcoma), HSA is a far more common cancer in dogs than in any other species, even though it is not the most common cancer found in dogs. It is estimated that HSA accounts for 5-10% of all tumors in dogs (angiosarcoma accounts for only about 0.01% of all tumors in humans). By comparison, lymphoma accounts for about 20% of all tumors in dogs, and mast cell cancer may account for an even higher percentage.

Is HSA hereditary?

No – or, at least, not exactly. The NCI (National Cancer Institute) definition of a familial (inherited) cancer is a cancer that occurs in families more often than would be expected by chance. Familial cancers often strike victims at an early age and may indicate the presence of a gene mutation that increases cancer risk. They may also be an indication of environmental or lifestyle factors shared by family members. Some breeds are at greater risk for developing HSA, and this risk is most probably due to heritable traits. But HSA is not heritable in the sense that affected parents would always pass it on to offspring. Some risk factors will probably be responsive to selecting which dogs to breed, but some risk factors may be firmly embedded in the breed (fixed traits).

When we talk about “risk”, each dog is independent from any other dog. If two golden retriever littermates (or four littermates, or eight littermates) develop HSA, it does not necessarily imply that this was a “high risk” breeding. If the cancers occur when the dogs are older adults, then those dogs need to be considered in the context of the whole population (or at least of their whole generation); more than likely these dogs fall in the population that were statistically likely to develop HSA (nearly 20% of Golden Retrievers). Likewise, in a litter of, say, seven Portuguese water dogs, if one were to develop HSA, the rest would not be “protected” by the expected 1 in 15 occurrence in a PWD litter. Risk does not work this way.

Imagine risk this way: Two people begin flipping coins at the same time. Both will get heads and tails about 50% of the time, but what Person A gets in a toss does not influence what Person B gets on the same or subsequent tosses – just like the result of one toss by any individual does not influence or predict the result of the next toss. Every toss is a 50/50 chance of heads or tails. The same is true of cancer risk and dogs.

A litter with multiple animals that developed a rare cancer at a very young age would trigger a high level of suspicion that there may be a heritable component related to the breeding or to one of the parents. However, this is not the case with HSA; in Portuguese water dogs, for example, the median age at diagnosis is about 10 years, just as we see in most other breeds.

Then, what heritable traits make some breeds more susceptible to HSA?

The bottom line is: we don’t know. We are actively asking this question in our research and through clinical trials.

My dog has been diagnosed with HSA. What are the treatment options?

The sites where hemangiosarcoma tumors most commonly arise are spleen, heart, and skin, but they may occur virtually anywhere blood vessels form. The standard of care is surgical removal of the primary tumor if there is no visible metastatic disease (determined through routine chest radiographs and abdominal radiographs or ultrasound), with adjuvant chemotherapy using doxorubicin. A couple of alternative protocols exist – for example, vincristine/doxorubicin/cytoxan – which seem to have about equal efficacy. Metronomic chemotherapy (lower doses administered more frequently) may be as effective as conventional chemo, but it does not appear to be better.

The principal reasons for surgery are to eliminate the major mass and source of tumor cells (especially when gross metastasis is not evident) and to reduce the chance of a lethal bleeding episode. The addition of chemotherapy is to delay recurrence from microscopic spread, which exists in virtually every dog diagnosed with HSA. Surgery alone has benefit (simply by reducing the probability of a lethal bleeding episode), and for some dogs it is curative (probably for those whose tumor has uncharacteristically remained confined to one site, as is often the case with skin tumors). Chemotherapy can be used alone in certain circumstances, when temporary palliation is desirable and surgery cannot be done (as for tumors in the heart that are considered inoperable.)

Choosing a therapy depends on several individual factors and preferences: how well the patient tolerates the medications (side effects), how often the patient can present for treatment, etc. An open dialogue with your veterinarian and oncology team is the best strategy for pursuing treatment for your dog’s particular case.

How long will my dog survive with HSA?

The median survival for dogs given standard of care for a primary tumor and no detectable metastases is about 180 days. Age does not seem to influence outcome. About 10-15% of dogs with HSA do remarkably well with treatment and have extended remissions. Some of these dogs go on to live full lives without recurrence; it seems that as they reach 12-14 months without recurrence, each day decreases the chance they will relapse. However, about 35% of dogs surviving longer than 4-6 months will fail to reach one year. And about 50% of dogs will die within 4-6 months of diagnosis. This is a very bad disease.

What signs or symptoms of HSA should I have noticed?

In all likelihood, none. Aside from visible skin tumors from the skin variety (which also tends to have the best outcome with treatment), HSA is a silent, insidious disease. “Warning signs” don’t appear until the situation is dire or even too late. The tumor itself does not cause pain or discomfort; the organs where the tumor usually grows are not highly innervated, and the tumor tends to invade areas where there is a lot of elastic tissue where its edging out of normal tissue does not cause apparent distress.

Isn’t there a test for HSA?

At present, there are no “early detection” tests that will predict an eventual diagnosis, and there are no simple laboratory tests that are highly specific and sensitive to diagnose HSA. Imaging plus biopsy is the only way to obtain a definitive diagnosis. Because there are other conditions that can resemble HSA on imaging, we strongly suggest that any dog have a biopsy (which could be collected during surgical removal of the tumor or affected organ) when there is a suspicion of HSA, and that the biopsy be processed and interpreted by an experienced pathologist.

There are several ancillary tests that could be used to guide if the need for surgery is immediate, but we do not recommend using these tests to make definitive patient management decisions. We do encourage owners to ask, “Why are we doing the test?” and “How do positive or negative results from this test help us?” and to inquire about testing options, just as they would inquire about treatment options.

Can my dog get HSA from plastic or rubber toys/Nylabones/food bowls?

There is no evidence to support a link between plastic, vinyl, or rubber products and cancer in dogs or in people. Because occupational exposure to vinyl chloride was recognized as an increased risk for HSA of the liver in people who cleaned reactors used in the manufacture of PVC, many people (and a few websites) mistakenly conclude that rubber and plastic products cause HSA. Finished PVC products are not the same as monomeric vinyl chloride, and despite newer concerns about softening agents in PVC products, no evidence supports them as being a cancer risk.

Are you looking for samples from my dog for your research?

Not at this time.