Breast Cancer Awareness Month: Canine Edition
By NAIA board member, Dr. Marty Greer, DVM, JD

Humans aren't the only animal to fall ill with breast cancer

How does hearing the words "she's got breast cancer" affect you? Bring tears to your eyes? Start a knot forming in the pit of your stomach? Make you want a second opinion? Create anger at being cheated?

We all know and have been affected by someone with this dreaded diagnosis. Maybe it is you, maybe someone you love: a wife, sister, girlfriend, mother, another family member or co-worker. We know it is a life-changing experience - pain, surgery, chemotherapy, radiation, fear of a shortened life expectancy.

For many women, they are fortunate that advances in early detection and medical therapy has made breast cancer a story of survival instead of a death sentence. But this is not the path for all those diagnosed.

Some are diagnosed too late or with a very aggressive form of the disease. Some cannot afford the medical care that allows for an improved prognosis. Some deny themselves the care they need.

But for those who are blessed with great diagnostics and treatment that allow for stories of happy endings, they owe their successes to the incredible research that led to this improved prognosis and outcome.

Part of the success story is thanks to the similarity of breast cancer in women with mammary tumors our dogs also are affected by. The dog has served as a research model for the disease in humans. Many advancements in human medicine are directly linked to the information discovered by research on the disease in dogs. Sadly, our dogs have not benefitted as much as humans have.

In human medicine, there are two keys to survival: early detection and successful treatment. Self-breast examinations and mammograms have been credited with changing survival by early detection. Many organizations have put their resources into educating us about the importance of these two important detection tools. New diagnostic tools are on the horizon for humans. Of course, mammograms are not available for our dogs. They rely on us to detect their lumps and to seek appropriate therapy for treatment.

Regular checkups and early detection are key factors for ensuring the long-term health of your pet

While the need for early detection is the same for both dogs and humans, treatment is a very different story. Despite the similarities between this human and canine disorder, there are no widely accepted successful chemotherapy and radiation therapy programs available for dogs. Surgical excision is the only treatment option widely available at this time for dogs.

In contrast to humans, mammary tumors in dogs are nearly 100% preventable if owners would take one simple step: to spay their female dogs prior to age 2 or younger. We all know that spaying (ovariohysterectomy or ovariectomy) prevents heat cycles and pregnancy. What we have not always done as well as we should have as veterinarians is to educate our clients that spaying under the age of 2 prevents most mammary tumors. Spaying before the first heat cycle protects nearly all dogs.

In the veterinary profession, we have also not educated our clients of the risks of spaying our female dogs. While it is true that spaying prevents pregnancy, mammary tumors, and pyometras, there is research that supports increased risk of other disorders thought to be related to removing the hormonal influence of the ovaries. There is an increased risk of urinary incontinence and associated urinary tract infections, osteosarcoma, hemangiosarcoma, and hypothyroidism. Each of these disorders has an associated health risk ranging from mild to severe affecting quality and length of life, as well as financial cost to the owner. Even when dogs with mammary tumors were included in the study, they still achieved greater longevity than their spayed female counterparts.

More information on the scientific literature that supports this can be found here and here.

These studies show that the decision to spay and when to spay an individual dog cannot be made without balancing the risks and benefits of the procedure.

As a group, veterinarians and animal control organizations have encouraged spaying, sometimes at a very early age, with the only goal being population control. We have overlooked the importance of individual dog health, meaning the health benefits of leaving our female dogs intact (i.e. not spayed). Instead, we have allowed public policy for the greater good of dog population control to dictate our decisions that we should spay and when we should spay our individual dogs.

A setting where your dog is comfortable can make an exam go more smoothly

Each individually owned dog should be considered an individual - there is not a one-size-fits-all way to approach this decision. More research needs to be done to aid in determining the optimal time for a spay.

For the dogs who are not spayed at this early age due to their inclusion in a breeding program or for other health benefits, early detection is still key in creating a favorable outcome for the patient and her family. Early detection in the dog is simple - it only requires a monthly examination by the owner and biannual examinations on palpation by her veterinarian. For dogs groomed frequently, professional groomers may be enlisted in this hands-on approach as well. This simple "pink paw" program will allow for early detection for nearly all mammary tumors. When detected early, surgical removal will usually lead to a cure.

Of course, for our dogs as for us, a healthy lifestyle with an appropriate diet, exercise, good weight management, preventive veterinary care, and the fortune of good genetics will allow for maximum longevity.

The same disorder we see in women and call "breast cancer" is called a "mammary tumor" in the dog. This terminology does not motivate owners to respond to this as a serious health threat to their dog. Although an accurate description, mammary tumor is too bland a term to use when a call to action is the best response.

We need to think of this malady in dogs as we do in women - a disorder that requires prompt surgical treatment. Since surgery is our only real option for treatment of "breast cancer" in the dog at this time, owners and veterinarians alike should opt for wide surgical excision of any suspect masses as soon as possible to improve long-term survival of the affected patient. (The only exception to this is in the rare case when inflammatory mammary carcinoma is suspected; in this case, surgical excision is not an appropriate treatment.) Taking a "let's watch it and see what it does" approach to a lump is likely to allow a treatable disorder to rage out of control and become a life-threatening disorder. Each heat cycle she has will likely lead to an increase in the size of the breast tumor.

There is a known strong correlation between the size of the dog and the size of the tumor and the malignancy rate - overall, 50% of mammary tumors in dogs are malignant. As in women, early detection and treatment leads to a much better prognosis and long-term survival rate.

As we know more about the prevention, early diagnosis, and treatment of breast cancer, we as well as our dogs can look forward to a long and healthy life free of this devastating disorder.