Molecular epidemiology has developed during the last two decades as an independent discipline at the crossroad of epidemiology and molecular sciences. On the one hand, molecular epidemiology aims to overcome the limitations of traditional approaches in epidemiology, by measuring events relevant to exposure, disease development, and response to therapy, reducing exposure and outcome misclassification, and identifying determinants of individual susceptibility to disease and treatment response. On the other had, it offers a framework for applying novel molecular techniques to population and clinical studies. Furthermore, the finalization of the HAPMAP project and the advent of new technologies for genotyping 100,000s of variants for limited cost have led to a new generation of studies aimed to identify cancer genes.
Recent technological advances and discoveries in genomic and molecular research, including in particular the use of microarrays and high-throughput analyses pose novel challenges to the design and analysis of molecular epidemiological studies, whose theoretical implications have yet to be fully explored. Molecular epidemiology, however, should not be seen as a mere application of novel molecular techniques to human studies, rather as a rapidly evolving field in which both epidemiologists, clinicians, molecular scientists - and even more so the new generation of 'molecular epidemiologists' with a multidisciplinary background - work together to address the most relevant aetiologic and clinical questions.
Cancer research has represented an area of particular importance for the theoretical development and the application of molecular epidemiology. The long duration of disease development, entailing the need to measure exposures back in the past, the heterogeneity of the relevant phenotypes, the complexity of carcinogenic pathways and the limited success in developing effective therapeutic strategies have traditionally represented major challenges to aetiological and clinical cancer research. The application of molecular techniques to epidemiological and clinical studies has therefore been seen as a potentially promising approach to overcome these limitations.