The Growing Importance of Veterinary Oncology

The Growing Importance of Veterinary Oncology: A Comparative Approach to Cancer Research
Veterinary oncology is a rapidly evolving field crucial for the health of our beloved animal companions and a vital area for comparative medicine. As pets live longer, the incidence of cancer in these animals continues to rise, presenting significant challenges and opportunities for veterinary professionals and researchers alike. This post delves into the compelling reasons why focusing on animal cancer is not only essential for animal welfare but also offers unparalleled insights into human cancer research, benefiting both species. This information is intended for veterinary practitioners, researchers, students, and pet owners interested in the scientific advancements and societal impact of veterinary cancer care.

Why Worry About Cancer in Pets?
Why should veterinarians be concerned about cancer in pet animals? Unfortunately, the prevalence of cancer in pet animals continues to rise. Prevalence is an increased number of diagnosed cancer cases per year without documenting the number versus the population at risk (incidence). This prevalence is increasing for a variety of reasons but is at least in part related to animals living to increasingly older ages.
Since cancer is generally a disease of the older animal, the price they pay for living longer is an increased likelihood of developing cancer. The greater life span is a result of better nutrition, vaccinations (preventing many previously fatal contagious diseases), better preventive and therapeutic medical practices, leash laws, and possibly a deeper devotion (human-animal bond) to pet animals within the last 10 to 20 years. With this increasing prevalence, veterinarians will be called upon more frequently to diagnose and manage the pet with cancer.
Cancer as a Leading Cause of Pet Mortality
Cancer is a major cause of pet animal death (Chapter 4). This statement is supported by a study that determined the cause of death in a series of more than 2000 necropsy cases. In that study, 45% of dogs that lived to 10 years or older died of cancer. With no age adjustment, 23% of patients presented for necropsy died of cancer. Of the more than 74 million household dogs and 90 million cats in the United States (AVMA), at least 4 million dogs and 4 million cats may develop cancer each year.
In a 1998 Mark Morris Foundation Animal Health Survey, more than 2000 respondents stated that cancer was the leading cause of disease-related death in both dogs (47%) and cats (32%). Another Morris survey done in 2005 revealed that cancer was by far the largest health concern among pet owners (41%), with heart disease the number two concern at 7%. Regardless of the exact numbers, cancer is one of the leading killers of pet animals and at the forefront of our clients’ thoughts as it relates to the health of their companions.
Public Awareness and the Human-Animal Bond
Breakthroughs in treatment of human cancer have received a great deal of exposure through the news media, popular press, and website information services. Although progress is slow, it does expose pet owners to what can be done and promotes an atmosphere of optimism. With this increased and optimistic media coverage, pet owners are becoming more knowledgeable and demanding in seeking care for the animal with cancer. The veterinary profession needs to be prepared for these demands.
More open acknowledgment of the human-animal bond has elevated the importance of pet animals to the level of human beings in many owners’ eyes. Some owners consider their pet more important than any human contact (Chapter 16, Section D). Proper health care of pet animals will be of increasing importance to many owners.
Cancer is a common and serious disease for human beings. Many owners have had or will have a personal experience with cancer in themselves, a family member, or a close friend. Realizing the importance of pets to owners, it must be realized that owners value the veterinarian’s ability to care as much as his or her ability to cure. Keeping this in mind, the veterinarian should approach the pet with cancer in a positive, compassionate, and knowledgeable manner. Frequently the veterinary profession has taken a negative approach (“test and slaughter”) to cancer. This attitude will not only be a detriment to the pet but may also negatively reinforce unfounded fears in the owner about the disease in humans. We owe it to our pet animal patients and their owners to be well informed and up-to-date on current treatment methods to prevent imparting unnecessary feelings of hopelessness.
Pets as Comparative Oncology Models
Pet animals with spontaneously developing cancer provide an excellent opportunity to study many aspects of cancer from etiology to treatment. The National Cancer Institute has recently approved the Comparative Oncology Trials Consortia (COTC), which is a collection of 14 veterinary schools united to perform clinical trials on dogs and cats with cancer. Access to new drugs and biologics of interest to the Children’s Oncology Group, National Cancer Institute, the Food and Drug Administration, and the pharmaceutical industry will speed clinical applications for both species. Providing these studies are done in a humane fashion, they may unlock clues to improving the outlook for this disease in both animals and humans.
Some of the aspects of pet animal cancer that enable attractive comparative models include the following:

• Pet dogs and cats are genetically outbred animals (like humans) as opposed to some strains of rats, mice, and other experimental animals.
• The cancers seen in practice are spontaneously developing as opposed to experimental carcinogen-induced cancers. Spontaneous cancers may behave in a significantly different fashion than induced or transplanted cancers.
• Pets share the same environment as their owners and may serve as epidemiologic or etiologic sentinels for the changing patterns of cancer development seen in humans.
• Pets have a higher incidence of some cancers (e.g., osteosarcoma, non-Hodgkin’s lymphoma, and others) than humans, allowing more cases to be studied.
• Most animal cancers will progress at a more rapid rate than will the human counterpart. This permits more rapid determination of end points such as time to metastasis, local recurrence, and survival.
• Because fewer established “gold standard” treatments exist in veterinary medicine compared to human medicine, it is easier and morally acceptable to attempt new forms of therapy (especially single-agent trials) on an untreated cancer rather than wait to initiate new treatments until all “known” treatments have failed, as is common in the human condition. Unfortunately, this latitude in clinical trials can be abused to allow diverse and unethical treatments to be attempted as well. We have an obligation to not deny our patients known effective treatment while at the same time planning well-designed prospective clinical trials of newer treatment methods. Investigations of new treatment methods are becoming more and more difficult to perform on normal laboratory animals because of the animal rights movement. This will make spontaneously occurring pet animal cancer a more attractive and morally acceptable research tool in the future but should not imply that poorly conceived and executed “research” is permissible on any animal.
• Pet animal cancers are more akin to human cancers than are rodent tumors in terms of patient size and cell kinetics. Dogs and cats also share similar characteristics of physiology and metabolism for most organ systems and drugs. Such correspondence allows better comparison of treatment modalities such as surgery, radiation, and chemotherapy between animals and humans to be made.
• Dogs and cats have intact immune systems as opposed to certain rodent systems or in vitro cancer studies, which allows immunologic assays and treatment approaches to be explored.
• Animal trials are generally more economical to run than human trials.
• Animals live long enough to determine the potential late effects of treatment.
• Regional referral centers exist to concentrate case accrual and facilitate clinical trials.
• Owners are often willing to allow a necropsy, which is a crucial end point for not only tumor control but toxicity.
• Dogs and cats are large enough for various imaging studies as well as surgical intervention.
• Radiation field sizes and chemotherapy doses and toxicity resemble those in humans.
• The recent elucidation of the canine genome and its resemblance and relevance to the human genome opens unique and unparalleled opportunity to study comparative oncology from a genetic perspective.
  Future Directions in Veterinary Oncology
  Owners who seek treatment for their pet animals with cancer are a devoted and compassionate subset of the population. Working with these owners can be a very satisfying aspect of a sometimes frustrating specialty. These owners are almost always satisfied with an honest and aggressive attempt to cure or palliate the disease of their pet, making the experience rewarding for the veterinarian, for the owner, and, most important, for the pet.
  Oncology also offers the inquisitive veterinarian a complex and challenging area for both clinical and bench research. The challenges and accomplishments in oncology have been very impressive. Oncology offers unlimited opportunity for the pursuit of knowledge for the benefit of animals and humankind. “Cancer, unlike politics and religion, is not a topic of controversy. No one is for it. Cancer is not another word for death. Neither is it a single disease for which there is one cure. Instead, it takes many forms, and each form responds differently to treatment.”
  Clinical and comparative oncology is a rapidly growing field of study. More training programs are being developed each year that will allow a wider distribution of experienced veterinarians into practice, research, industry, government, and the academic setting. Through study and treatment of pet animal cancer, the veterinarian can hopefully impact both the pets afflicted with this disease and its development and treatment in humans.

AI Image Prompt: A compassionate veterinary oncologist examining a golden retriever, with a subtle overlay of abstract scientific elements like DNA strands and cancer cells, representing the intersection of clinical care and comparative oncology research. The setting is a modern, clean veterinary clinic.
Source Citation:
Researcher: Stephen J. Withrow, David M. Vail
Thesis Title: Withrow & MacEwen’s Small Animal Clinical Oncology
Supervisor: N/A
University: N/A
Year of Completion: 2007
Exit Page Number: xvii
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