Personalized medicine: a patient - centered paradigm

An editorial about personalized medicine should perhaps start with a definition. Although several versions of such definition exist, we pay homage here to the oldest definition reported in modern medical literature. Sir William Osler (1849-1919) recognized that “variability is the law of life, and as no two faces are the same, so no two bodies are alike, and no two individuals react alike and behave alike under the abnormal conditions we know as disease”. Modern day medicine recognized this fact and implemented its ethos since inception of its practice separating it from a general “one-size-fits-all” approach. A medical doctor would ask the patient about his/her suffering and prescribe a treatment suited to the patient’s condition. Individualized evaluation and treatments, which include history taking, focused examination and specific laboratory and medical tests have now become routine in day-to-day medical practice. Personalized medicine, takes into account the needs of individual patients, and provides custom-tailored therapeutic approaches. More recently, modifying life style approaches as part of a broad preventive medicine orientation, are gaining popularity and yielding positive results. Weight management, smoking cessation and healthy diet are well-established preventive strategies that have a contributed a great deal in reducing mortality associated with chronic diseases. But there are challenges. For example, losing weight is easy. But, maintaining it at an optimum level is a challenge! Similarly, limits of existing diagnostic and therapeutic strategies are becoming well-known. Despite all the impressive advances in imaging technology, advent of new medical diagnostics, and burgeoning of therapeutic interventions, the widespread prevalence of disability and premature mortality associated with chronic conditions such as diabetes, cancer and heart disease continues to frustrate scientists and clinicians alike. There are also many unanswered questions. Here is one such question. Why two patients with exactly the same diagnosis and identical test results respond differently to the same treatment. Have we reached a glass ceiling? Are we limited in our scientific understanding of disease and health? Rapid advances in genotyping and genomics might shed some light. Let us look at example of the oral anticoagulant drug Warfarin that is used for the long-term management of thromboembolic events. Studies have shown that of over 21 million patients, who are on Warfarin in the USA, some suffer from its adverse effects [1] and others don’t. Why? Research has shown that there is a variant nucleotide in the Cytochrome P450 CYP2C9, which is responsible for this variation observed in the drug response [2]. Other genetic variations that alter the personal response to Warfarin also exist in the Vitamin K epoxide reductase complex protein 1 (VKORC1) [3]. The U.S. Food and Drug Administration (FDA) has recognized and acknowledged the importance of genotyping CYP2C9 and VKORC1 during Warfarin treatment [4,5]. In doing so, it has given the field of genomics a tremendous boost. Let us take a look at another example. Trastuzumab is a very effective drug for breast cancer treatment. However, only 10-20% of the breast cancer patients can benefit from it. This is due to the fact that Trastuzumab is based on monoclonal antibodies targeting the Epidermal Growth Factor Receptor (HER2/neu/EGFR) [6]. Therefore only patients with amplification (multiple copies) of HER2/neu/EGFR will respond to this treatment. The availability of Trastuzumab has created a research drive at a frantic pace, to standardize the detection of HER2/ neu/EGFR amplification, for which several methods are now available. The utility of genomics in personalized medicine is gaining popularity. Its potential for predicting disease occurrence is receiving worldwide attention and illustrated by examining the relationship between certain * Correspondence: loc2008@qatar-med.cornell.edu Genetic Medicine Department, Weill Cornell Medical College in Qatar, Qatar Foundation, Education City, P.O. Box 24144, Doha, Qatar Full list of author information is available at the end of the article Chouchane et al. Journal of Translational Medicine 2011, 9:206 http://www.translational-medicine.com/content/9/1/206