A tool known as a liquid biopsy—which finds signs of cancer in a simple blood sample—promises to solve those problems and more. A few dozen companies are developing their own technologies, and observers predict that the market for the tests could be worth billions.
The technique typically homes in on circulating-tumor DNA (ctDNA), genetic material that routinely finds its way from cancer cells into the bloodstream. Only recently have advanced technologies made it possible to find, amplify and sequence the DNA rapidly and inexpensively.
Right now, the tests, which are available from several companies, mostly aid in treatment decisions for people already diagnosed with a particular form of cancer, such as prostate or lung. ut the liquid tests can also provide services that tissue biopsies cannot. Repeated tests could potentially detect disease progression or resistance to treatment long before it would trigger symptoms or appear on imaging. Tissue biopsies examine only selected bits of tumors and can thus miss cells that have turned more dangerous than their neighbors; in principle, the liquid biopsy can detect the full spectrum of mutations in a mass and thus indicate when more aggressive treatment is needed. And importantly, liquid biopsies may one day provide a fast, easy screening test for detecting a cancer and determining its type in people who seem perfectly healthy.
For the tests to enter wide usage, clinical trials must prove that the approach detects cancer accurately and that by aiding in treatment decisions, it improves progression and survival rates.
*Editor’s Note (6/26/17): This sentence was edited after posting. The original erroneously stated Illumina spun off from GRAIL.
