Precision Medicine and the Health of the Public
By Ana Diez-Roux, MD, PhD, MPH
March 24, 2016
Dean and Distinguished Professor of Epidemiology, Dornsife School of Public Health
There is much talk these days in the medical world about precision medicine. President Obama announced the Precision Medicine Initiative (PMI) over a year ago in his State of the Union address on January 20, 2015. As defined by the White House, "the Precision Medicine Initiative will pioneer a new model of patient-powered research that promises to accelerate biomedical discoveries and provide clinicians with new tools, knowledge, and therapies to select which treatments will work best for which patients." The Initiative was launched with a 215 million dollar investment including 130 million for the National Institutes of Health (NIH) to establish a national voluntary cohort of patients to participate in various research efforts and 70 million for the National Cancer Institute (NCI) to identify genomic drivers in cancer and apply that knowledge in the development of more effective treatments. The objectives of the PMI include more and better treatments for cancer, the creation of a national voluntary research cohort that would be broadly available for a range of research questions, as well as a commitment to protecting privacy and the promotion of regulatory modernization and public–private partnerships, all of which are expected to facilitate the initiative as it moves forward. But what does it mean for public health?
Identifying better treatments and targeting treatments more precisely so that they are more effective is certainly an important goal. The PMI relies heavily on cancer and more specifically cancer treatment as a guiding paradigm for what it aims to accomplish. Not only does it allocate 70 million dollars to cancer genomics research, it also relies on cancer examples to justify the need for the "precision medicine approach" more broadly. Genetically targeted therapies have been identified for a number of cancers with promising results. It may indeed be true that the greatest promise of genomics lies not in predicting disease risk but in targeting therapies once disease occurs (an area sometimes referred to as pharmacogenomics). An assumption of the PMI is that the principles of the genetically targeted treatment approach to cancer can be extended to a range of other health conditions. It is argued that embracing the approach and promoting research that can identify personalized treatments can have a large impact on clinical practice and through clinical practice on population health broadly.
What does the PMI mean for public health? Should we as public health academics and practitioners embrace the approach? The first challenge of course is that, despite some language about “precision” prevention, the initiative (as reflected in the examples used to justify it) it is heavily focused on the treatment of disease after it occurs. This is very different from the public health approach that emphasizes prevention as key to shifting population patterns. But a second perhaps more fundamental difference between the PMI approach and public health is the notion that improving health requires a fully “individualized” approach that targets treatments (and prevention efforts) specifically at each individual based on his or her characteristics. The underlying paradigm here is clearly the tailoring of treatments based on genetic make up. In the PMI an effort is made to extend this notion to prevention (as well as treatments) and to broaden the set of individual-level factors used to tailor the treatment beyond genes to also encompass something loosely referred to as individualized behaviors and environments. This is quite different from the traditional public health approach that emphasizes moving beyond individually-targeted approaches to include interventions on physical and social environments that affect the population as a whole.
It is difficult to argue with the basic principle of precision medicine, i.e. that prevention and treatment strategies may benefit from taking individual variability into account. Certainly, in the clinical realm, this is an important principle that doctors have often informally (and regrettably often without supporting evidence), attempted to implement. Whether this strategy is cost-effective is an issue that remains to be determined. Regardless, building evidence in support of effective individually-targeted strategies is of course an important goal. But a very different question is whether an approach that emphasizes individual tailoring and that treats (or prevents) disease in each individual, one at a time, holds great potential for improving population health (or for reducing health disparities) more broadly. Geoffrey Rose said this many years ago when he articulated the basic principles of preventive medicine, that mass diseases have mass causes and that shifting population distributions of health and disease requires addressing these more distal environmental factors that affect us all.
So should public health turn its back on precision medicine? Absolutely not. The notion that individual factors are important to health and should be considered in developing prevention and treatment strategies is fully consistent with a public health approach. It is also positive that the PMI recognizes the relevance of factors beyond genes, such as behaviors and environments (albeit rather vaguely defined, underdeveloped, and treated analogously to genetic makeup despite radical differences between genes and these other types of health determinants). But precision requires more than targeting individual-based approaches. It is about understanding and acting on the appropriate levers. The precise characterization of the drivers of health in individuals requires consideration of factors outside of individuals that affect individuals through a multiplicity of mechanisms. Improving health (for individuals and populations) requires intervening on these drivers in a precise way. In some cases targeting individuals will be appropriate and sufficient but in many cases we will need to act in other ways using strategies that go well beyond the realm of medicine. This is the type of precision in understanding and precision in action that we need to significantly improve population health. And this is what public health is really about.