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Obama thinks "precision medicine" will make us healthier. Experts are skeptical.

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The White House is committing $215 million to support efforts to develop personalized medicine, a priority the President touched on in his State of the Union earlier this month.

At the time, the details weren't clear. But today the White House released more information on the "precision medicine initiative," which has bipartisan support: it would get started with a $215 million cash injection from the 2016 federal budget to support everything from the building databases at the National Institutes of Health to study the genetic bases of disease, to applying that knowledge to targeted cancer therapeutics and public health.

"Most medical treatments have been designed for the 'average patient,'" the White House statement read. "As a result of this 'one-size-fits-all-approach,' treatments can be very successful for some patients but not for others."

The only problem is that this is much, much harder than it sounds.

Precision medicine — also known as personalized or individualized medicine — has been one of the big, unmet promises in health care for a long time. Hank Greely, a law professor at Stanford, put it this way: "It's been the hot thing coming for almost 20 years." Writing in the New York Times, Mayo Clinic physician-researcher Michael Joyner called it a "moonshot" medical research project, summing up: "Unfortunately, precision medicine is unlikely to make most of us healthier." He's right.

Here's an explanation of what personalized medicine means — and why it's mostly still a long ways off:

Personalized medicine would build off genetic testing

Let's start with the basics: everyone's cells contain chromosomes made up of chemical strands called DNA, which carry genetic information. These genes are recipes for proteins that give you the wide variety of traits that make you who you are, from the curl of your hair to the texture of your earwax to the color of your eyes.

Health care professionals have long been able to conduct genetic tests to look for these variations in our DNA. These tests might tell you whether you have a genetic condition or are at risk of developing a disease. For example, a doctor might test for mutations in genes called BRCA-1 and BRCA-2, which are linked to breast and ovarian cancers, to understand if a patient is at a higher-than normal risk for these diseases.

The next step would be to tailor treatments to DNA
Angelina Jolie

Angelina Jolie, who famously got a double mastectomy after discovery she carried genetic mutations that put her at a higher risk for breast cancer. (Getty Images)

That's where personalized — or precision — medicine comes in. In theory, doctors could use genetic tests to tailor medical treatments to the specific biology of patients.

"We each have genetic variants that put us at increased or decreased risk of getting various diseases, or that make us more or less responsive to specific treatments," the Mayo's Dr. Joyner succinctly explained in the Times. "If we can read someone's genetic code, then we should be able to provide him or her with more effective therapeutic and preventive strategies."

Take breast cancer. Say you have a history of this disease in your family, or you're from an ethnic group that's predisposed. Your doctor could order a genetic test that would look for mutations of BRCA-1 and BRCA-2. If you test positive, you would then work with a physician and/or genetic counselor to decide how to proceed. You may opt for a preventive mastectomy (as Angelina Jolie famously did), or make lifestyle changes that mitigate your risk of cancer and get mammograms more frequently than other women who don't carry the mutation.

Or consider Lynch syndrome, an inherited illness linked to colorectal cancer. There are several genes associated with Lynch syndrome, and if you test positive, you might begin getting colonoscopies in your 20s rather than your 60s — a screening regime that is tailored to your particular genetic risk instead of the general population. Again, health care tailored to your genes.

Advocates say that this targeted ("precision") approach would be safer and more effective than the current "one-size-fits-all" medicine. But critics argue that we don't yet understand enough about the human genome (and how it interacts with the environment and other factors) to routinely use genes as the basis for medical decisions.

Personalized medicine could get even more advanced

In his State of the Union address, Obama flicked at another, more recent form of personalized medicine — pharmacogenomics — when he said drugs have successfully treated some cystic fibrosis patients.

Pharmacogenomics uses genetics to predict an individual's response to a drug. Proponents say this is the future of pharmaceuticals — since a person's genetic make-up can impact how and whether they respond to medications. They argue that using genes to guide treatments would lead to more effective therapies.

With cystic fibrosis, for example, a drug a drug called ivacaftor (brand name Kalydeco) was recently approved by the Food and Drug Administration for about 4 percent of patients who have a particular genetic mutation that causes the deadly and chronic lung disease in them. It's the first drug to treat the genetic cause of CF — but only in people with the mutation.

Another promising area of pharmacogenomics has been cancer therapeutics. Cancer has its own DNA and genetic mutations, and there are some drugs that target those — as opposed to just giving a patient radiation that would not be as precise. In these cases, patients are tested for genetic variations and then prescribed therapies for their tumors. One example is Herceptin for the treatment of breast cancer in women with a gene known as HER2/neu. A doctor will test a breast-cancer patient to see if she is HER2/neu positive, and if she is, consider prescribing Herceptin as a treatment.

All these treatments are still incredibly costly

Not so fast, though. There are big barriers here between the dream of pharmacogenomics and the reality. For the most part, the science of genetics just isn't refined enough to help most patients, and developing targeted therapies is hugely expensive and time-consuming.

For example, Bill Gardner at the Incidental Economist ran some numbers on the promising cystic fibrosis therapy: "It took 24 years and tens of millions of dollars to get from the discovery of the CFTR [the particular genetic mutation that causes CF in some people] to the FDA approval of a drug. Moreover, this drug was designed for a mutation found in only a small fraction of the population of an already rare disease."

Gardner noted that the drug costs about $300,000 per year, not only because of the manpower and years of research behind it, but because the market for the drug is small: "Precisely because the treatments are targeted at phenomena at the level of specific harmful mutations, they are not just personalized but practically bespoke, and correspondingly pricey."

Even if they weren't so expensive and challenging, the Mayo's Joyner writes in the Times, "for widespread diseases like diabetes, heart disease and most cancers, no clear genetic story has emerged for a vast majority of cases."

Easy to gather characteristics — like age, sex, and body weight — are still better predictors of Type 2 diabetes than any genetic test. For the risk of lung cancer, we may not have a genetic test or targeted therapy in mainstream medicine yet — but we do know smoking puts most people at a higher risk for early death and disease.

So as you can see, personalized medicine is the future, but getting targeted therapies and treatments into the hands of most Americans is much further afield than Obama might like to admit.