Cancer and comparative imaging.

Comparative oncology research is gaining traction as a method for streamlining the drug discovery and development strategies currently in place worldwide. This approach uses the tumor-bearing pet dog as a relevant and complementary model alongside the traditional use of rodents, no-human primates, and other large mammalian species such as purpose-bred dogs or pigs. To date, most comparative oncology studies have been designed and executed to evaluate new anticancer drugs using tumor-bearing dogs with specific naturally occurring cancers as models for humans. These studies have proved extremely valuable for modeling pharmacokinetic-pharmacodynamic relationships, refining drug doses and schedules, and validating an individual drug's target in vivo. The National Cancer Institute's Comparative Oncology Trials Consortium (http://ccr.cancer.gov/resources/cop/COTC.asp) is a cooperative effort that provides infrastructure and resources to support this effort. To complement ongoing efforts in this field, we propose expansion of comparative cancer imaging as a component to drug discovery and development. Diagnostic imaging is critical to diagnosis and management of malignancy in both humans and animals. Molecular imaging techniques allow for detection of disease-specific signals that provide individualized data to aid in patient selection, response to therapy, and prognostication. In this review, we will highlight the comparative oncology studies that have used molecular imaging techniques, demonstrating the value of spontaneous canine cancers as a research tool in drug and imaging agent development.