Cancer, in the pet population, is a spontaneous disease. Pet owners, motivated by the desire to prolong their animals' quality of life, frequently seek out the specialized care and treatment of veterinary oncologists at private referral veterinary hospitals and veterinary teaching hospitals across the country. Therapeutic modalities for veterinary cancer patients are similar to those for humans, including surgery, chemotherapy, radiation therapy, and biotherapy.
Mission: The Comparative Oncology Program (COP) will serve as an example of an integrated comparative oncology program and will provide a mechanism by which naturally occurring cancer models can be used to generate new information about cancer, translate biological concepts regarding cancer to relevant in vivo models, and bring novel therapeutic options to the management of human cancers.
It has been estimated that there are approximately 65 million dogs and 32 million cats in the United States. Crude estimates of cancer incidence indicate that there are roughly 6 million new cancer diagnoses made in dogs and a similar number made in cats made each year. This large population of pets with cancer provides the opportunity to study spontaneous cancers similar to those seen in humans.
Examples of such spontaneous models include non-Hodgkin's lymphoma, prostate carcinoma, lung carcinoma, head and neck carcinoma, mammary carcinoma, melanoma, soft tissue sarcoma, and osteosarcoma. Many factors contribute to the value of these spontaneous cancers as relevant models for human cancer:
- These animals share many environmental risk factors with their human owners, suggesting their value as sentinels of disease.
- These cancers share tumor biology and behavior with human cancers and, in some cases, have identical tumor histology and response rates to conventional chemotherapy.
- In most cases, the prevalence of these cancers is sufficient for clinical trials and biological studies (i.e., osteosarcoma and non-Hodgkin's lymphoma)
- The size of dogs and cats makes multi-modality protocols feasible; the lack of "gold standard" treatments allows early and humane testing of novel therapies.
- The rapid progression and early metastatic failure allow rapid completion of clinical trials.
The value of these spontaneous cancers in understanding and managing cancer in general has been evident to veterinary oncologists and other cancer researchers for many years. More than 30 years ago, optimization of bone marrow transplantation protocols was undertaken in pet dogs with lymphoma. Since then, the work of clinical veterinary oncologists in using naturally occurring cancers in animals to better understand and treat cancer in humans has been referred to as comparative oncology.
Today, comparative oncologists are using naturally occurring cancers to:
- Understand environmental risk factors for cancer.
- Examine genetic/familial determinants for cancer predispositions seen in some dog breeds.
- Develop and optimize novel cancer and gene imaging systems.
- Evaluate novel therapeutic strategies for a variety of cancers.
- Add biological relevance to genomics data generated from microarray and other molecular techniques.
Examples of studies using comparative approaches to cancer investigation are presented below. Common to these investigations is the understanding that the study of spontaneous cancers in dogs will contribute to a better understanding of cancer in general. Examples of the use of comparative oncology within the NCI's Center for Cancer Research (CCR) are also presented.
Recent examples of comparative oncology studies
In the cancer research community, the awareness of naturally occurring cancer models is relatively limited. Broader awareness of these naturally occurring cancer models is needed, as are greater opportunities for collaboration and interaction between comparative oncologists and the cancer research community. A centralized resource for currently active comparative oncology programs and for investigators not currently involved in comparative oncology is now necessary.