"Instead of placing all patients with small tumors in the same early-stage category, as physicians currently would do, we can now assess their risk based on the tumor's genomic profile," Nevins said. "The current system of 'staging' lung cancer tumors will eventually become obsolete."
To employ the test, physicians take a sample of the tumor as it is removed during surgery. They extract its "messenger RNA," which represents the activity of thousands of genes in the tumor. Messenger RNA translates a gene's DNA code into proteins that run the cell's activities. Hence, it is a barometer of a gene's activity level inside the cell.
Scientists label the messenger RNA with fluorescent tags. The fluorescent RNA is then placed on a tiny glass slide, called a gene chip. There, it binds to its complementary DNA sequence on the gene chip.
When scanned with special light, the fluorescent RNA emits a telltale luminescence that demonstrates how much RNA is present on the chip ?and thus which genes are most active in a given tumor. The physicians then use a rigorous statistical analysis to assess the relative risk of large grouping of genes, called metagenes, which have similar characteristics.
The test generates a risk "number" for each patient. If their risk exceeds 50 percent, the patient is advised to get chemotherapy.
"This new genomic test is a clear example of personalized medicine, where we use the unique molecular characteristics of each patient's tumor to guide treatment decisions," said Geoffrey Ginsburg, M.D., Ph.D., a professor of medicine and co-author of the study.
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Source:Duke University Medical Center