Pets Fighting Cancer

Understanding Pet Cancer from a Veterinarian's Perspective

An In-Depth Look with Dr. Ingrid Pyka

Sadly, as with their human counterparts, animals also fall victim to cancer. Oncology (the field of cancer) encompasses a vast amount of information; this article is only a brief summary.

What Is Cancer?

Tumors and cancers are terms used for cells of the body dividing without restraint. Benign tumors are groups of such abnormal cells that remain confined to one focal area. Benign tumors do not spread to other parts of the body. Malignant tumors, however, contain cells that have the ability to uncontrollably grow deep into the tissue from which it begins, as well as having the potential to spread (metastasize) to other tissues and organs. Widespread metastasis will occur when the cancer cells travel through the blood stream and/or the lymph (immune) system reaching other parts of the body to start up new “colonies” of cancer.

To help determine the severity of a patient’s cancer—once diagnosed, the disease is staged. Staging and grading of tumors will vary with different cancers but, in general, Stage I has only local involvement, while Stage II affects the nearest lymph node. Stage III indicates widespread disease throughout the body.

Specific attributes of the cells may determine the cytological grading which allows further defining of the cancer and its characteristics. A lower or higher stage may not always mean a better or poorer prognosis (probably outcome), but staging and grading will assist in determining the potential treatment course(s).

Who Gets Cancer?

Boy hugs black Labrador retriever

Unfortunately, every animal has the potential for cancer. Most cancers develop with mid-aged to older animals, but, it is not unheard of in young patients. Though no cancer follows an iron-clad rule, certain breeds do have a higher predilection to some tumor types. Large and giant dogs, for example, have a stronger likelihood of osteosarcoma (bone cancer). Boxers have an increased risk for mast cell tumors.

In other instances, environment or other conditions dictate the potential risks. For instance, dogs and cats spayed before their first heat cycle have a dramatically lower rate of mammary cancers (breast cancer). White cats that go outdoors with sun exposure significantly increase their chances of acquiring squamous cell carcinoma (a slow, but aggressively ulcerative skin malignancy).  Not to minimize the importance of properly vaccinating your pet, some vaccines have been implicated in causing local tumors as well.

Your veterinarian will be able to guide you with certain risk factors your pet may have for specific cancers.

How To Tell If Your Pet Has Cancer

Certainly, the earlier a tumor is diagnosed, the better the chances for effective treatment and possibly even a cure. Vigilant owners and veterinarians have saved pets by addressing growths or other subtle changes as soon as they noticed them.

Black cat

Unfortunately, despite the best screenings, many cancers are all too often not found until advanced stages. This may be due to the rapid onset of growths or the more subtle cancers that are virtually undetectable with our conventional screening tests, until they have advanced to a progressive stage.

The best preventive medicine is annual veterinary visits and, depending on the age and breed of your pet, even semi-annual veterinary visits. If you find new lumps or note any changes in your pet, including weight loss, inappetance, or just vague signs of “not feeling right,” have your veterinarian assess your pet as soon as possible. A thorough physical examination is the best initial screening for many health issues. When warranted, your veterinarian will recommend further diagnostics, such as blood and urine tests, ultrasound and/or x-rays. These are all effective tools in detecting apparent abnormalities with the organs, including cancer.

Once your veterinarian suspects or has found a tumor, he or she may perform a biopsy (sampling of the tissue) for microscopic evaluation. Only the identification of the cells will give a definitive diagnosis. Biopsies may require a mere needle prick to collect some of the involved tissue cells or surgery to remove a larger sample of tissue. It is not uncommon for treatments to be delayed until a final diagnosis and staging is assessed.

What Can Be Done Against Cancer?

Fortunately, research has made great advances in veterinary oncology and the number of veterinary oncology specialists is rapidly growing. Owners have many new treatment options for their pets.

Local tumors, such as a small mast cell skin lesion or a single hemangioma nodule on the spleen, may respond well to simple surgical excision, often with no further recurrences. Surgery may also be used to debulk (make smaller) the initial cancer site, with other cancer treatments to be implemented secondarily.

Dog lays on veterinary table

Chemotherapies involve the use of drugs generally geared to stop or slow down the abnormal replication of the cancerous cells. Chemotherapeutic drugs may include, among others, hormones (e.g., prednisone), “alkylating” drugs (e.g., cyclophosphamide, chlorambucil), plant-derived drugs (e.g., vincristine), and even some antibiotics (e.g., doxorubicin).

Often, “chemo” programs utilize a combination of multiple chemotherapeutic drugs managed with very specific schedules. Some of the medications may be given by the pet owners at home. Others, due to high toxicities, must be administered by trained veterinary staff in a special facility with carefully monitored handling and disposal of the materials. The patient may require longer hospital stays until the chemotherapeutic drug has safely passed.

Fortunately, animals do not seem to react with the intense ill side-effects as humans frequently do, making chemotherapies a much more tolerable treatment course for pets. Systemic reactions and toxicities (low blood cell counts, anemia, kidney and/or liver failure, etc.) do remain serious risks throughout these protocols, necessitating frequent monitoring tests as recommended by your veterinarian.

Radiation therapy also has its place in battling cancers in animals. Used often along with other treatment modalities, radiation kills cancerous tissue and can be quite successful for certain local lesions, such as oral tumors or squamous cell carcinoma. It carries its risks as well, primarily with repeated anesthesia and potential damage to nearby non-cancerous tissue (though with newer pinpoint technology this has dramatically decreased). Unfortunately, radiation therapy is limited in veterinary medicine simply due to the relatively small number of available facilities.

The use of hyperthermia, cryosurgery and photo therapy has also shown positive responses for certain tumors. Still in earlier stages of research, immune mediated (vaccine-like) treatments have great potential as well. In addition, specific nutritional changes and homeopathic/herbal approaches have given owners even more options to fight their pets’ cancer.

The Cancer Patient

Some cancers have successful cures, reaching life-long remission. Unfortunately, other malignancies have poor cure rates, in spite of excellent medical care. Each patient has their own different responses as well. Some owners choose not to put their beloved pet through any treatments. Others elect to try every therapeutic option even for just a few more weeks with their companion. How to or whether to pursue treatment with a veterinary cancer patient is a highly personal decision that each family, given the appropriate information, must make on its own.

In the profound advances in today’s veterinary medicine, the treatment opportunities have provided incredible options in extending the lives of our companion animals.

Fortunately, even in the untreatable cases, now we can at least provide the best quality of life during the terminal phase of cancer. We do have multiple modalities to help alleviate discomfort and pain management. And, thankfully, research still promises more success in fighting cancer in the future.