External influences are dominant in cancer development, so why is it important to understand the role of genetic variation in this disease?

While the role of the environment is undoubtedly important, it is rarely the sole determinant of cancer risk. Rather, it is the interplay between the environment and our genes or, more specifically, the variations found in our genome, that result in differing responses to the environmental exposures and lifestyle factors that can lead to the onset of cancer. The genomic revolution has given us the tools to examine common genetic variants in a comprehensive manner, allowing us to evaluate the effects of modest or small changes in a gene's function or expression that may contribute to cancer risk. New technological advances make it possible to survey a well-chosen set of common genetic variations and identify markers of disease risk. However, these findings must be further validated in successive replication studies before we can begin to investigate the functional consequences of genetic variation.

Given the genetic and molecular research currently under way, what might cancer prevention look like 5, 10, or 20 years from now?

We cannot fully anticipate the future course of cancer prevention, but we are in a position to make at least a few educated guesses. The value of genetic testing and counseling should continue to increase over time, along with our knowledge base, as we conduct more clinically relevant studies. One can envision a day when individual profiles of genetic risk factors may help to inform lifestyle choices or to accelerate the rate of screening for early detection of specific cancers. Furthermore, the identification of genetic mechanisms and pathways underpinning cancer will provide insights into the development of new diagnostic, preventive, and therapeutic measures. Still, we should be wary of underestimating the complexity of cancer and, for this reason, continue to pursue integrated approaches that bring together observations across many disciplines - including genetics, cancer biology, and epidemiology - to advance cancer prevention research.