Personalized Genetic Test Offers New Way to Track Cancer

BY Jenny Marder  February 19, 2010 at 10:50 AM EST

By mapping the genetic code of malignant tumors, researchers have developed a new technique to identify and track cancer: a blood test derived from a patient’s unique DNA.

The finding is the latest in a growing field of personalized medicine, which researchers hope will someday lead to cancer treatments tailored specifically to individual patients. The study will be published in the Feb. 24 issue of the journal Science Translational Medicine.

To develop the test, researchers used samples of healthy and cancerous tissue from four colorectal and two breast cancer patients. They mapped the entire genetic code of each, and then combed through data to identify chunks of scrambled DNA in the cancerous tissue — a mark of cancer.

The focus on chunks of DNA rather represents a shift from past research, which has generally looked for changes in single DNA letters in cancerous cells. But chunks of scrambled DNA are easier to identify in the blood.

The blood tests — which are patient-specific — detect cancerous cells in the blood by identifying these genetic biomarkers. By measuring the level of the markers, the researchers could tell whether the patients’ cancers had returned or spread. The hope is that doctors could use the tests to determine whether a patient is free of cancer, or to identify the best kind of treatment to pursue for each patient.

“It’s another step in the movement toward being able to diagnose cancer at the genome level,” said Dr. Matthew Meyerson, a professor of pathology at Harvard Medical School. “It potentially paves the way toward being able to follow the progress and presence of cancer in a blood test.”

Still, the authors acknowledge that although the price of gene sequncing is falling each year, the test is still too expensive to be put into widespread use. They estimated its cost at about $5,000.