The Dog Cancer Survival Guide (103 page)

HSA is an aggressive and highly metastatic malignancy. More than half of dogs already have detectable spread when they are diagnosed, and may feel sick or even experience internal bleeding.

The standard of care for HSA is surgery, followed by chemotherapy (usually doxorubicin). Depending upon the tumor’s location, radiation may also be used after surgery to avoid recurrence. Radiation is particularly indicated for skin or subdermal HSA with narrow or incomplete margins.

When you need to look up the definition of a word or phrase, find it listed in
Chapter 5
, which begins on
page 46
.

New approaches for care are being investigated, and we need them, because the long-term prognosis for dogs with HSA of the internal organs is poor: one to three months for dogs who receive surgery and six months for dogs who receive surgery and chemotherapy. Dogs with non-ruptured spleens (stage I) may live a few months longer. About ten percent of dogs who receive standard treatment live one year past the initial diagnosis.

Dogs with skin HSA generally have an improved median survival time, depending upon the stage of the cancer.

HSA develops in the endothelial cells, which line the interior of the blood vessels. The blood vessels – arteries, veins, and capillaries – carry blood throughout the body, through their vast and complicated network. Nearly every tissue needs blood, so every cell is close to a blood vessel of some sort. The sheer enormity of the blood circulatory system is one reason why HSA tumors can develop anywhere in the body.

The spleen is the most common location for HSA; in fact, two-thirds of dogs who have splenic masses have cancer, and two-thirds of those cancers are HSA. This pattern is commonly referred to as the two-thirds rule.

The right atrium of the heart is the second most common site for HSA, accounting for 40% of all heart cancers and making HSA the most common heart tumor. Other common locations are the skin, under the skin (in the hypodermis or subcutis), the muscles and, rarely, the liver (liver lesions are more likely metastasis than primary tumors). HSA, which occurs in the spleen, the liver and/or in other internal organs, is referred to as visceral HSA.

Over half the number of dogs with HSA have detectable spread at the time of diagnosis, because HSA is so very aggressive and metastatic. It spreads both locally, into the tissues around the primary tumor site, and distantly, through the blood stream. Cancer cells can also spread directly into the abdomen if the tumor is bleeding or ruptures, which is called transabdominal transplantation. It’s more common for HSA to metastasize through the bloodstream to the lungs, abdominal lymph nodes, omentum (a fatty organ found throughout the abdomen), brain, bone and muscle.

HSA is usually seen in middle-aged and older dogs; its precise cause is not known.

Subcutaneous and visceral tumors inside the body occur most frequently in the Golden Retriever, German Shepherd and Labrador Retriever.

HSA heart tumors most frequently occur in the Golden Retriever, German Shepherd, Rottweiler, Greyhound and other large-breed dogs.

Skin HSA is associated with light exposure, specifically UV or ultraviolet light. Skin tumors typically develop in areas with no or very sparse hair, and more frequently in breeds with thin coats and light-colored skin, including Pit Bulls, Whippets, Boxers and Dalmatians.

In one study of over 1, 300 dogs, neutering appeared to increase the risk of cardiac tumor in both sexes. Intact females were least likely to develop a cardiac tumor, whereas spayed females were most likely to develop one.

Dogs often feel sick when they are first diagnosed with HSA. Owners usually bring them in for a variety of vague symptoms, such as a loss of appetite, decrease in energy, weight loss, vomiting or diarrhea. Upon examination (palpation, abdominal X-rays or abdominal ultrasound), the vet often finds an enlarged spleen, which is a red flag for visceral HSA. Occasionally, a mass is found during a routine physical exam, when the dog is otherwise asymptomatic. At other times, an ultrasound or X-ray, performed for other health issues, detects the masses.

Dogs with a more advanced splenic cancer may have much more dramatic symptoms, caused by a ruptured or bleeding tumor. If a tumor has ruptured, dogs may experience sudden and severe weakness or a total collapse, which is a potentially life-threatening situation. A splenic rupture causes anemia (low red blood cell counts) and internal bleeding into the abdomen, which is called hemoabdomen. A hemoabdomen can cause a distended belly, circulatory failure, uncontrolled internal bleeding, abnormal heart rhythms and a clotting problem, called disseminated intravascular coagulation (DIC). DIC is a serious blood disorder: first the proteins controlling blood clotting become abnormally active, creating small blood clots, and then abruptly stop clotting altogether, leading to uncontrollable bleeding.

If HSA has developed in the heart, the tumor may bleed into the pericardial cavity. The pericardium is a tough sac that completely encases the heart and protects it from internal damage by producing small amounts of pericardial fluid, which acts as a cushion. When a tumor bleeds, or effuses, into this sac, it can put excess pressure on the heart and actually impair its function. In this case, dogs may have vague signs like loss of appetite, weight loss and low energy – or more severe conditions, like an anemic collapse or even heart arrhythmias. When too much fluid builds up, it can cause a potentially fatal crisis, called tamponade: the pericardium has become so full that the heart no longer has room to beat – the chambers cannot fill with blood, or pump it out effectively. If your dog collapses or loses consciousness, prompt and dramatic intervention is required.

HSAs that develop in the skin are typically smooth, hairless, raised bumps ranging in color from dark red to purple. They are normally found on the belly or other areas with sparse hair, although both their location and appearance can vary. It’s important to understand that while they are called “skin HSA,” these tumors can be found in all skin layers, including the subcutaneous tissues and the muscle underneath.

When HSA is suspected, a thorough physical examination must be performed. Your vet will certainly look for an enlarged spleen, which may be discovered during a routine palpation of the abdomen. When there is hemoabdomen (internal bleeding), a fluid wave may also be detected: a literal “wave” that moves across the belly when it is gently pressed.

An enlarged spleen found on abdominal X-rays should be confirmed with an abdominal ultrasound, which provides more information about the internal organs than do X-rays, including which organs have masses, possible metastatic lesions and the amount of abdominal fluid.

If abdominal fluid is seen, it should be sampled (aspirated) to determine whether it is blood. Cancer cells are rarely present in the aspirate, so, while it cannot typically confirm HSA, it can confirm potentially dangerous internal bleeding.

While it is standard to aspirate spleen, heart and liver masses discovered on ultrasound, these masses should not be aspirated when splenic HSA is suspected. Cancer cells are rarely present in aspirate, and because HSA is an inherently bloody cancer, aspirating masses can cause potentially dangerous bleeding and tumor rupture. As confirmation of HSA with aspiration of masses is rarely possible, this procedure is not worth the risk. The rare exception is when a suspicious lesion does not appear to have many blood vessels. Superficial masses, such as skin and regional lymph nodes, suspected for HSA represent a low risk for life-threatening bleeding, so these masses should be aspirated to confirm the diagnosis.

Aspirates are rarely able to confirm the presence of splenic HSA, so the standard confirmation for this type of cancer is a surgical biopsy that removes the entire spleen.

If heart HSA is suspected, an echocardiogram (an ultrasound of the heart) is the best way to diagnose the mass. This produces the most detailed view of the heart and its structures, but masses in the right atrium, which is where HSA often occurs, are hard to see for the inexperienced eye. When it comes to these masses, your best bet is to get an experienced cardiologist to do the echocardiogram and interpret the results. When there is visible pericardial effusion on the echocardiogram, it should be aspirated and examined for cancer cells, even though the results of this test are often unreliable for confirming HSA – malignancies are not found at all in three out of four samples.

Why do I recommend a pericardial aspirate, if it doesn’t usually help diagnose HSA? There are several good reasons. For one, it
can
diagnose lymphoma, another cancer likely to show up in the heart. Lymphoma is highly treatable with chemotherapy, so when found, treatments can be started immediately. Also, the pH level of the sample can be evaluated, which can help to predict whether cancer is present – although this is not definitive, in itself (its usefulness is debated amongst oncologists).

Furthermore, if the echocardiogram fails to confirm a mass, the aspirate of the pericardial fluid may reveal elevated levels of a protein called cardiac troponin I. This marker rises with the incidence of heart muscle ischemia (lack of blood) and necrosis (cell death), both of which occur with pericardial effusion, and even more so in dogs with cardiac hemangiosarcoma. CardiacTropin I tests are not routinely run in most hospitals; your vet may be able to get it through a specialized lab, if he thinks it will be useful.

Finally, removing the fluid from the pericardial sac will temporarily alleviate symptoms and stabilize your dog. This is often the most important reason to do this procedure.

Regardless of the site of the primary tumor, we typically look for spread right away, with the first X-rays and ultrasounds of the most common sites: the liver, lungs, mesentery and omentum (abdominal organs), heart, kidney, brain, muscles and lymph nodes. Half of the dogs suspected for HSA already have detectable spread at diagnosis, and knowing the stage of the cancer is helpful when making treatment decisions later.