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January 11, 2016

Unique cancer mutations show up in microscopic fragments of DNA in a patient’s blood, which can give physicians a telltale sign of the presence of the disease in almost all types of cancer mutations — within cells or floating freely in the bloodstream.

The “liquid biopsies,” as the tests are known, have become something of a Holy Grail in cancer treatment among physicians, researchers and companies betting big on the technology.

Liquid biopsies — unlike traditional biopsies involving invasive surgery — rely on an ordinary blood draw. Advances in sequencing the human genome, enabling researchers to detect genetic mutations of cancers, have made the tests possible.

As recently as a few years ago, the liquid biopsies were rarely used except in research. Today, thousands of the tests are being used in clinical practices in the United States and abroad, including at the M.D. Anderson Cancer Center in Houston; the University of California, San Diego; the University of California, San Francisco; the Duke Cancer Institute and numerous other cancer centers.

Researchers at Hopkins and 23 other cancer centers did a survey in 2014 of liquid biopsies in 846 patients with 15 different types of cancer, and the tests revealed cancers in the blood of 80 percent of those with advanced cancers, but only 47 percent of those with localized disease.

“The results showed that in early-stage cancer, we still have some work to do,” Velculescu said. “In those cases, repeating liquid biopsies may be needed.”

The liquid biopsies also appear to work better in some cancers than others. The tests, for instance, appear to be less effective in detecting brain cancers, partly due to the blood-brain barrier, a natural defense system that regulates the passages of substances between blood and the brain.