Dispelling the myths of veterinary cancer and its treatment (Proceedings)


Dispelling the myths of veterinary cancer and its treatment (Proceedings)

Often, the primary clinician may be the veterinarian making a diagnosis of cancer in a pet and performing the initial client education regarding their pet's disease. Critically important, life-or death decisions regarding euthanasia, treatment, choice to pursue referral, etc. may be made based on information that the owner gets from their primary veterinarian. There is still a great stigma attached to a diagnosis of cancer, and it is natural for owners of pets with cancer to anthropomorphize and equate cancer treatment in animals with experiences they may have had with treatment of themselves, their friends or family members. Being able to succinctly address these concerns and "dispel" some of the myths that owners may have is critical component of cancer management in the primary care setting. There are, additionally some myths or misconceptions that veterinarians and staff cling to that may alter their approach to the cancer patient or the information they impart.

Is cancer really a problem in pets? Unfortunately, yes. It is the leading "natural" cause of death in dogs, and the 2nd or 3rd most common cause of death in cats. Up to 50% of dogs and 30-35% of cats will be affected by some type of tumor in their lifetime.

Why does is seem like there so much more cancer in pets these days? Better pet health care = longer life. We are getting so good at managing other husbandry-related conditions in dogs (nutrition, infectious/parasitic disease, keeping pets indoors and on leashes) that they are now living long enough to develop more geriatric conditions such as heart disease, kidney disease, endocrine disease, and cancer.

Did something in the environment play a role in my pet's cancer? Was I feeding the wrong food? There have been some weak associations proposed between certain types of cancer and environmental influences (canine lymphoma and certain herbicides or living in urban environments, canine mesothelioma and asbestos, feline gastrointestinal lymphoma and environmental tobacco smoke), but in the vast majority of cases no such association can be made. Thus, for the most part, food additives, lawn chemicals, pesticides, cosmic rays, etc. do not seem to significantly increase an animal's risk of cancer.

Why treat animals with cancer? Because we can! We treat many animals with chronic disease that are never cured (Diabetes, other endocrine diseases, heart disease), and cancer is another chronic disease. Furthermore, cancer is a disease that we can sometimes cure! Even in cases where cure is unlikely, there are many cancers where we can extend an excellent quality of life with treatment.

Do we have to do XXX for this lump now? Can't we just wait and see what happens? Owners may use this phrase regarding initial diagnostics (let's wait and see if it grows), additional surgery or other treatments to prevent local recurrence after incomplete excision (let's wait and see if it grows BACK), or therapy to delay or prevent metastasis (let's wait and see if it spreads). Let's wait and see if it grows: In general, delay in achieving a diagnosis only serves to increase the difficulty of surgery and, potentially, the likelihood of metastasis. Larger tumor size is statistically associated with worse outcome for several important veterinary cancers, including canine and feline mammary carcinoma and canine melanoma. The lump they are dealing with may very well be nothing, but if it is a tumor, the time to find that out is sooner rather than later. Let's wait and see if it grows back: Locally recurrent tumors are statistically associated with a worse prognosis in certain diseases such as canine mast cell tumor and oral melanoma, and suspected of being worse in others such as feline vaccine-associated sarcoma. For this reason, the time to get aggressive is the very first time the tumor occurs. Let's wait and see if it spreads: In general, treatment of gross metastatic disease is palliative at best. Asking drugs to kill a big bulky tumor is asking a lot, but asking those same drugs to have an effect against microscopic tumor cells in the lung or lymph node may be a much more reasonable goal. For example, the approximate median survival time for dogs with osteosarcoma undergoing amputation, but not receiving chemotherapy until the time of metastasis, is approximately 4 months whereas dogs receiving chemotherapy for microscopic metastasis immediately after surgery is approximately 12 months.