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Personalized Medicine Revolution Gains Momentum

Biomarker research paves the way to precision cancer medicine.

BY SUSAN JENKS
PUBLISHED TUESDAY, MARCH 4, 2014
Her doctor calls her his “miracle child,” even though she’s over 60, the mother of two adult sons and a grandmother of three. But Vera Lynn Coe, or “just Lynn” as she prefers, has survived advanced breast cancer for nearly a dozen years—a medical milestone few reach.

The Cocoa, Fla., resident says she has always maintained a positive attitude, even when refusing to limit her options to palliative care after learning her breast cancer had spread to her liver. Instead, she chose to undergo chemotherapy while she continued working. After surgery, she took Herceptin (trastuzumab), a drug that targets HER2, a protein in her cancer cells that fuels rapid growth. Within a few months, her cancer went into remission.

“It locks the gates on my tumor cells,” Coe says of Herceptin, describing how it prevents tumors that produce too much of the HER2 receptor to gain a survival edge. Because she tested positive for this molecular biomarker, her physician knew immediately that she had a particularly aggressive cancer and that her cancer would likely respond well to this targeted therapy.

The biomarker that guided Coe’s treatment is one of several dozen cancer-associated biomarkers considered “actionable” by clinicians. Some biomarkers, such as HER2, are predictive, meaning they can be used to predict how a patient will respond to treatment. Others are prognostic, meaning they can be used to estimate how a disease will progress. Still others are diagnostic—they can be used to confirm a diagnosis even in its earliest stages. Broadly defined, biomarkers refer to an array of biological molecules in the body, which take many forms—genes, their protein products and the organic chemicals inside cells—that can be objectively measured and evaluated, in the blood, urine, other bodily fluids or tissues, to distinguish normal from abnormal processes and indicate the presence or severity of disease. Biomarkers can be inherited, such as certain genetic mutations, or acquired, such as damage to DNA that occurs from certain exposures.

In cancer, these biological substances are playing an increasingly important role in helping doctors “personalize” medicine, tailoring treatment to each individual’s genetic fingerprint. Molecular mutations inside tumor tissues can help predict responses to certain therapies, as in Coe’s case, or flag differences between aggressive and indolent disease, allowing some patients to avoid or delay chemotherapy. With the aid of other tests, biomarkers can also confirm the early presence of disease or monitor treatment for a risk of recurrence. In blood tests, biomarkers can reveal an inherited vulnerability to certain cancers, including breast and ovarian cancer and a familial type of colon cancer.

As a screening tool in an asymptomatic general population, the bar is high for finding biomarkers unique enough to detect cancer at its earliest, most curable stages while at the same time resulting in the fewest possible false alarms, making it an intensive research goal.

Cancers are Darwinian. The cancer may get better for short periods of time, but then it returns.

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