Utilization of genomic signatures to direct use of primary chemotherapy

The success of treatment of cancer patients depends on matching the most effective therapeutic regimen with the characteristics of the individual patient, balancing benefit against risk of adverse events. The primary challenge in achieving this goal is the heterogeneity of the disease, recognizing that breast, lung, colon and other cancers are not single diseases but rather an array of disorders with distinct molecular mechanisms. Genomic analyses, and in particular gene expression profiling, has been shown to have the capacity to dissect this heterogeneity and afford opportunities to match therapies with the characteristics of the individual patient's tumor. Here we review the success in developing gene expression signatures that have the capability of predicting response to various commonly used and newly developing cancer therapeutics. We further discuss the challenges and the opportunities in utilizing these tools in present-day clinical practice.