With the advent of microarrays, pharmacogenomics research has entered a whole new level of sophistication. This technology allows researchers to study patient populations, collecting expression patterns of tumors before any treatment is given.

By analyzing treatment outcomes, scientists hope to identify expression patterns that can accurately predict a good response to treatment. In the future, before any treatment is given, doctors may be able to predict a patient's response to chemotherapy or radiation based on this research. This could eliminate much clinical "guesswork." One day, simply by looking at expression patterns found in a single blood sample or a small tissue biopsy, doctors may be able to tell a patient which of the available drugs or radiation treatments will work best and which will not. Clinicians will be better able to plan effective therapies at the proper doses for individual cancers.