Precision Medicine and the Future of Health Care

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In 1546, Girolamo Fracastoro published a new idea that challenged current thinking on the cause of disease.1 For centuries, Galen’s theories of humorism had been the basis for medical diagnosis and treatment. Imbalances in the bodies’ humors (blood, bile, sweat, etc.) and miasmas (i.e., bad air) were believed to bring sicknesses like cholera, flu, or plague. Galen’s thinking had guided medical thought and practice from the second century, into the 1800s. In a radical departure from Galen’s theories, Fracastoro suggested that fomites, small particles, were invisible causative agents of disease. It was not until Koch and Pasteur later isolated bacteria in the late 1800s that medical practice evolved based on this new understanding. We now possess incredible power to examine the structure and function of the human body. Moreover, we can use that information to guide a multitude of pharmaceutical or surgical interventions. But, there remains a gap in our ability to predict and to prevent disease, and that is the next fundamental advance that we are poised to address through advances in human genetics.
In January 2015, President Barak Obama announced the Precision Medicine Initiative.2 Now, 2 years later, the program is beginning to take shape and gain momentum. The precision medicine initiative is a program that intersects advances in laboratory and clinical genetics with large-scale clinical informatics to better understand biological, environmental, and behavioral factors that influence health and wellness. Not only can this insight be useful to define specific treatments for individual patients, but it can also be used to inform public health and health policy.
This grand scientific challenge has the potential to fundamentally move the practice of medicine away from current models where doctors are trained to monitor and treat diseases in similar ways for groups of patients, toward new models based on disease prediction and preventive interventions that are specific to individual genetic and environmental considerations. Precision medicine will also challenge us to redefine the basis for evidence-based practice. At its core, evidence-based practice already values individual patient preference and autonomous participation in medical decision making by patients. However, much of the current thinking that defines high-quality evidence prioritizes large prospective cohort studies, where individualized treatments would be lost in the average response. This will require some shift in thought and practice to accommodate a new reality where the best practice among individuals is a different approach in every case.
Precision medicine has been decades in the making and is the next step in our use of genetics to shape biology, health research, and clinical practice. The majority of advances in genetics research—the description of DNA and elucidation of its double-helical structure, interpreting its coded messages, mapping the human chromosomes, sequencing the human genome and much more—has mostly occurred since the early 1950s. The current goal of precision medicine is to leverage our understanding of genetics and disease to provide individualized treatments. The most notable advances have come in cancer therapy where clinicians and scientists are now able to target malignant cells with unprecedented specificity. What is also emerging is a growing appreciation for the importance of the interaction between genetic material and the environment: epigenetics. While early studies of genetic diseases have had some success pinpointing defective sequences, the majority of the most common diseases do not appear to be explained so simply. In many cases, it is not enough to have a defective gene buried deep within the genome; one must also have the necessary confluence of other contributing factors to manifest the disease.
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