A key theme that emerged at the Think Tank was that, as with any scientific endeavor, the analytical challenges of GxE studies can only be met by first elucidating the underlying scientific question and rationale. Broadly, examples of scientific rationale for GxE interaction studies in epidemiology can include: discovering novel genetic or environmental risk factors; providing etiologic insight; and providing guidance on public health and clinical strategies for cancer prevention, intervention and treatment [Hunter 2005; Thomas 2010]. Throughout the Think Tank discussion a distinction was drawn between the goal of characterizing joint effects of known or putative genetic and environmental risk factors, and the goal of discovering novel genetic loci by leveraging GxE interactions. In a translational epidemiology framework, where the translational pathway is defined on a five point scale from T0 (scientific discovery research) to T4 (translational research from practice to population health impact) [Khoury, et al. 2010], discovery can be framed within the T0 (scientific discovery research) phase, and characterization within the T1 (translational research from discovery to candidate application) phase.
