For more than two years: Genetic tests and personalized medicine

For more than two years, Jody Uslan had been taking the drug tamoxifen in hopes of preventing a recurrence of breast cancer. Then a new genetic test suggested that because of her genetic makeup, the drug wasn't doing her any good.

"I was devastated," she said. She stopped taking tamoxifen, and is now evaluating alternative treatments.

Experts say most drugs, whatever the disease, work for only about half the people who take them. For the others, their genetic makeup makes the drug ineffective, e.g., because the person may lack an enzyme to process the drug appropriately. The hope of "personalized medicine" is that doctors will be able to consider the likely effectiveness of a drug for a particular patient in light of that person’s relevant genes, in deciding which drug to prescribe.

Scientists are learning about a growing number of genetic markers that determine the likely effectiveness of particular drugs. Some genetic tests are available, many at a cost of several hundred dollars. The Food and Drug Administration has formally recommended genetic tests to guide the selection or use of some drugs, but has not yet made formal recommendations on many others.

Advice: To avoid the side effects, cost, and nuisance of using certain drugs unnecessarily, talk to a genetic counselor if you use Herceptin (trastuzumah), Erbitux (cetuximab), Vectibix (panitumumah), chemotherapy for breast cancer, Tamoxifen, Ziagen (abacavir), Camptosar (irinotecan), Tegretol (carbamazepine), Coumadin (warfarin), or Celebrex (celecoxib). Ask the counselor whether you should have a genetic test to determine the drug’s likely effectiveness for you.

Read another story about the value of genetic counseling.

Thanks to Andrew Pollack for the source article in today's New York Times.