In medicine, one size doesn't fit all. Two people who take the same cancer medication, for instance, may have very different responses. One may have severe, even life-threatening side effects, while the other experiences few if any side effects and seems to sail through treatment. Or, the drug may shrink a tumor in one person but not in another.
How could two people have such drastically different reactions to the same medication? Chalk it up to genes. People inherit variations in their genes. And even slight variations can have a profound effect on how your body responds to certain medications.
Today, a handful of tests are available that can detect some of these genetic variations and predict how you're likely to respond to certain medications. Doctors are already using some of these tests to help customize treatment based on a person's specific genetic variations, particularly in the area of cancer. This practice is called personalized medicine. Here's a closer look at personalized medicine, how it's applied today and what the future may hold.
Whole article: "Mayo Clinic":[ http://www.mayoclinic.com/health/personalized-medicine/CA00078]