Bridging science and clinical practice: how to use molecular markers when caring for a patient with brain cancer

Technical advances in genomic and proteomic profiling and bioinformatics have resulted in the identification of a large number of possible prognostic, predictive, and diagnostic molecular markers in glial tumors. Increasingly, clinical trials are incorporating tissue analyses to prospectively and retrospectively study the value of these and yet-to-be defined markers. Once validated, markers form the basis for increasingly stringent classification schemes and the development of personalized, targeted therapies. Descriptions of molecular marker findings, many not validated as clinically relevant, are filling pathology reports, and patients arrive to clinic with the latest journal article requesting marker assessment. Although some practitioners may choose to incorporate these findings into clinical decision making, empirical data supporting these decisions is limited to a few specific circumstances. This article reviews three markers-codeletion of 1p/19q, methylation of the O6-methylguanine-DNA methyltransferase (MGMT) promoter, and the presence of IDH1/2 mutation-for which there exists high or moderate levels of evidence of current clinical utility for guiding diagnostic, prognostic, and treatment decisions.