Developing the evidence base for cancer chemoprevention: use of meta-analysis.

Meta-analysis is a quantitative approach for systematically combining the results of previous studies in order to arrive at conclusions about the body of research. It answers a specific research question, includes an explicit methodology section, employs strategies to minimize bias, yields objective findings and enables evidence-based decisions. In this review, we examine meta-analysis taking examples from the field of cancer chemoprevention, an innovative area of cancer research that focuses on the prevention of cancer through pharmacological, biologic, and nutritional interventions. In particular, we consider the practical steps involved in the conduct of a meta-analysis, illustrate the statistical techniques for the calculation of summary estimates, present the available methodology for detecting and minimizing bias and, finally, we discuss unresolved issues and future applications.