ABSTRACT
The main prognostic factors for early-stage breast cancer (ESBC) include tumor size, nodal status, hormone receptor status, HER2/neu status, histology, and tumor grade. While these and other prognostic factors have been incorporated into treatment guidelines, the remaining prognostic uncertainty means that some patients destined to recur do not receive adjuvant therapy and others are unnecessarily treated experiencing only unnecessary side effects. Clearly better prognostic tools are needed to guide treatment decisions in patients with ESBC (1). New, highperformance screening techniques using DNA microarrays have permitted the analysis of patterns of gene expression in thousands of genes simultaneously. Several investigators have reported efforts to define gene expression signatures based on their ability to predict the risk of disease recurrence and guide the use of adjuvant systemic therapy in ESBC. Before the role of such assays in actual clinical practice can be fully understood, a careful evaluation and validation of test performance in a variety of settings is essential. Such an evaluation ideally precedes the wide scale dissemination and utilization of new diagnostic and prognostic technologies.
