Personalized medicine: the time is now; six years after scientists successfully sequenced the entire human genome, the results are changing nearly every aspect of medicine

National Women's Health Report, March, 2009

"There have been some spectacular successes with genetic information that are beginning to have a significant impact on the care and treatment of patients today," says Geoffrey S. Ginsburg, MD, PhD, who directs the Center for Genomic Medicine in the Duke Institute for Genome Sciences & Policy in Durham, NC.

One of the most significant areas affected is cancer treatment. "The ability to evaluate cancer patients on the basis of the molecular fingerprint of their cancer is readily available today," Dr. Ginsburg said. That information is then used to more effectively target treatments, many of which are so expensive that some insurers actually require genetic testing before approving their use.

Some of the greatest impact of personalized medicine for women can be seen in breast cancer. Today, pathologists identify the genetic makeup of the tumor, the results of which help the oncologist determine treatment. For instance, a genetic test called Oncotype DX rates the likelihood of recurrence. If the odds are small, the oncologist may not recommend chemotherapy or radiation. (24)

Conversely, if the tumor tests positive for the HER2 protein, which is produced by the HER2 gene and causes cancer cells to grow faster, you know you have a more aggressive cancer and are a candidate for trastuzumab (Herceptin). If your tumor expresses estrogen, then you are a candidate for the antiestrogen treatment tamoxifen. However, before giving you the drug, your doctor might test for genetic changes in your CYP2D6 gene. This gene makes an enzyme called 2D6, required to transform tamoxifen into the cancer-attacking antiestrogen endoxifen. But a mutation in the CYP2D6 gene can render those enzymes inactive or only moderately active, making tamoxifen fairly worthless. (25)

The area of pharmacogenetics--or selecting drugs on the basis of the genetic underpinnings of the disease or the patient--is growing so fast right now, says Dr. Ginsburg, that the FDA has begun requesting such testing for certain drugs.

In 2007 the agency updated the labeling for the blood thinner warfarin (Coumadin) to urge health care professionals to test for genetic mutations in the genes CYP2C9 and VKORC1. Patients with variants in these genes metabolize warfarin differently, increasing the risk of blood clotting or life-threatening bleeding if they don't receive the proper dose." "With genetic information, we can be more precise on the dosage and better manage these individuals," says Dr. Ginsburg.

According to Dr. Ginsburg, "personalized medicine can do more than improve care. It can also improve quality and reduce costs," he says.

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On the other side of personalized medicine are genetic tests for specific mutations linked to disease, like mutations in the BRCAl and BRCA2 genes that significantly increase a woman's risk of breast and ovarian cancer. For years, people worried that learning their genetic risk for these diseases could lead to job and insurance discrimination. But in May 2008, President Bush signed into law the Genetic Information Nondiscrimination Act (GINA), which protects Americans from being treated unfairly because of genetic differences that may affect their health. The law prevents discrimination from health insurers and employers. The health insurance part should become effective in May and the employer part in December. (27)

The passage of GINA is an important milestone for research as well as individual privacy, says Dr. Ginsburg, MD, PhD. "Not only will it allow individuals to get their genetic information and know that it's not going to be used against them for employability or insurability, but it will also lower the barrier for them to participate in critical studies needed to move this agenda forward."