Personalized medicine relies upon individualized diagnosis that provides molecular information delineating optimal therapeutic strategies. For many diseases, but especially cancer, the development of predictive biomarkers requires performing assays directly on the diseased tissue or tumor. The last decade has seen the explosion of both prognostic and predictive biomarkers in the research setting, but few of these biomarkers have entered widespread clinical use. This article examines issues concerning tissue-biomarker development and the hurdles faced in reaching the goal of truly personalized medicine. Targeted therapy guided by predictive biomarkers is possible; however, for significant progress, researchers need to focus on three key issues: robust assays for the clinic, validation in clinically relevant environments and assuring appropriate analytes are available for these new assays.
Treatment of life-threatening and chronic diseases has changed dramatically in the last two decades. Patients who either would have lost their life or would have been incapacitated are now living productive lives thanks to the new drugs, monoclonal antibodies and treatment regiments that the biotechnology revolution has provided. Unfortunately, side effects, toxicity and an inability to determine which agent provides optimal therapy continue to hamper optimal patient care, and contribute to the expense of care, as well as the cost of drug development. The proposed solution to this problem is development of a new generation of biomarkers that will predict response to these new agents; what is termed personalized or individualized medicine. At present, the development of new therapeutic agents outstrips the development of cognate predictive biomarkers.