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Written by leading veterinarians to provide you with the information you need to care for your pets.

The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Cancer: Imagining the Worst, and the Best

Imagine taking your dog for his usual morning walk. Nothing seems out of the ordinary; your companion’s energy level and demeanor is perfectly normal, as it's been for as long as you can remember.

Imagine leaving for work, or to run errands for a few hours, and returning home to find your pet completely lethargic and unable to rise, breathing shallow rapid breaths, with a distended abdomen, pale gums, and an exceedingly rapid heart rate.

Imaging rushing to the nearest open veterinary hospital, and within moments of arriving, hearing the devastating news that your pet is suffering from internal bleeding from a mass associated with its spleen, and will require emergency surgery in order to have any chance of survival.

Now imagine hearing the mass very likely represents a deadly form of cancer called hemangiosarcoma, and that with emergency surgery, this disease is typically fatal within 2-3 months, and even with aggressive chemotherapy after surgery, survival is extended to only about 4-6 months.

While trying to wrap your head around this information, imagine hearing there is a smaller chance the bleeding results from a completely benign tumor that will be cured with surgery alone. And there is no way to know whether your dog has a cancerous or benign tumor before making the decision to go to surgery. What do you do when all you can think is, "My dog was completely normal this morning when we went for a walk"?

Hemangiosarcoma is a fairly common cancer diagnosed in dogs. It arises when mutations occur in the endothelial cells lining blood vessels. The most common primary sites of tumor development include the spleen, the right atrium of the heart, and the skin. The liver is also a common site for a tumor to form, and also a frequent site for metastases from other locations. Hemangiosarcoma occurs more commonly in older dogs, especially larger breeds such as Golden retrievers, German shepherds, pointers, Boxers, and Labrador retrievers.

As hemangiosarcoma tumors grow, rapidly dividing endothelial cells try to form blood vessels and vascular channels, but their growth is erratic and abnormal, and tumors are fragile and prone to bleeding. If bleeding occurs while a tumor is small, or the cancerous vessels can be repaired, dogs will usually be asymptomatic. Once a tumor reaches a critical size, bleeding will typically be more severe and dogs will show signs related to massive internal blood loss.

In most cases, owners have no way of knowing their pet is afflicted with this type of cancer until it is very advanced and they are literally faced with a life or death decision about how to proceed.

The statistics surrounding a diagnosis of hemangiosarcoma are fairly abysmal. It is estimated that over 80 percent of affected pets have microscopic metastases at the time of diagnosis. Therefore, even though the surgery to remove the immediate source of bleeding is life-saving, it is generally not curative. Chemotherapy can prolong survival, but typically only for a short duration. Even when dogs are diagnosed with hemangiosarcoma "incidentally," meaning tumors are discovered before dogs show signs of bleeding, the average survival time with surgery alone is about 6-8 months.

The unluckiest dogs have visible metastases in multiple organs at the time of their diagnosis. Survival times for those dogs may only be on the order of a few short weeks.

What I find most problematic is there is little information to help determine whether a splenic mass is cancerous or not before a tissue biopsy is obtained, so owners are forced to make a decision about pursuing emergency surgery without having all the information they might need to feel completely educated about their choice. Although most splenic tumors are ultimately diagnosed as hemangiosarcoma, other types of cancers can occur within this organ, many of which carry a more favorable prognosis than the odds I’ve listed above.

I’ve also seen dogs "diagnosed" with hemangiosarcoma within their spleen, with spread to the liver, based on images obtained with an ultrasound. Yet biopsy showed the masses in both organs were completely benign.

Hemangiosarcoma is uniquely challenging for this exact reason: Owners are forced to make major decisions with limited evidence-based data to feel comfortable they are truly making the "right" choice for their dog.

I’ve treated many dogs with hemangiosarcoma and happily continue to monitor a small number of patients who are alive a year or more after their diagnosis. I’ve talked with their owners about the spectrum of emotions they experienced when deciding whether or not to proceed with the initial emergency surgery. The most common answer I hear is they just knew they had to give their dog a chance. They felt that should something happen during or after surgery, they would be content knowing they made their decision with their pet’s best interests in mind. And they knew that even though the odds for long-term survival were not in their favor, the odds for a chance to have a few more usual morning walks were great enough to warrant the risk of a diagnosis of cancer.

Of course, there was always the hope the tumor would be benign, but even when hemangiosarcoma was confirmed, they were comfortable knowing it wasn’t the duration of time that mattered for them, but the time itself.

Whether dealing with cancer or with any other of life’s infinite challenges, I think we could all stand to benefit from approaching things from a "quality over quantity" standpoint. And really figure out what it means to enjoy the moment while it lasts.

Dr. Joanne Intile

Image: Petar Paunchev / via Shutterstock


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