Molecular profiling of breast cancer.

Purpose of review This review is a comprehensive survey of molecular-profiling literature published since 2004. Recent findings More microarray-based gene-expression profiles that are prognostic for breast cancer have been published, strengthening the possibility that the microarray gene-expression profile may indeed provide clinically meaningful results. Requirement for snap-frozen tissue, however, will continue to be a limiting factor in clinical application. Results from a multicenter validation study were less spectacular than the original findings. A prognostic model based on classical markers performed well in a comparative study. Further clinical validation, with a large sample size, is needed. A prognostic gene-expression profile of 21 genes, which can be assayed using routinely processed formalin-fixed paraffin-embedded tumor tissue, has been introduced and this assay has also been shown to correlate with degree of benefit from chemotherapy. Two large clinical trials to validate gene-expression-based assays are to be launched in North America (TAILORx) and the European Union (MINDACCT). The usefulness of these genomic tools is still being debated, because clinicopathologic factors also are still important. Summary Gene-expression-based prognostic tests are now available as commercial reference laboratory tests. Their successful implementation will depend on the seamless integration with existing clinicopathologic markers.