The Race to Diagnose Cancer With a Simple Blood Test

Liquid biopsies could transform cancer care as we know it

Ron Winslow
OneZero
Published in
12 min readJan 3, 2019

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Illustration: Eric Petersen

FFive years ago, a team of researchers pored over the results of a prenatal genetic test given to more than 125,000 healthy pregnant women and made a stunning discovery. The blood test, marketed by gene-sequencing giant Illumina, was designed to detect chromosome anomalies associated with conditions such as Down syndrome by analyzing fragments of fetal DNA circulating in the mother’s blood.

In 3,757 of the tests, the scientists found at least one abnormality. But in 10 of those cases, further analysis revealed that the fetuses were in fact normal.

“In every one of those 10 cases, it turned out there was an undiagnosed cancer” in the mother, says Alex Aravanis, who at the time of the study was the senior director of research and development at Illumina.

To Aravanis and the other scientists, the unexpected result suggested a whole new opportunity: a single blood test for detecting multiple types of cancer before a person has any symptoms. “This was really important background science that [suggested] this might be possible,” says Aravanis, a founder and chief scientific officer at Grail, a Menlo Park, California–based startup launched three years ago by Illumina.

A so-called pan-cancer blood test would address a major barrier in substantially reducing the toll of the world’s second leading killer: Most cancers are diagnosed at advanced stages, when the prognosis is poor. Catching cancer early, when it has the best chance of being cured with surgery, could, theoretically, prevent cancer deaths and reduce the high costs of treating the disease.

“We do very well in improving lives of people whose cancers are screened and detected before symptoms occur,” says David Ahlquist, MD, a gastroenterologist at Mayo Clinic. “Five-year survival rates increase dramatically if cancer is detected at an early stage.”

But most cancers — including some of the most lethal — aren’t prevalent enough to justify regularly screening for them in healthy people. At least not with current methods. But in an October article published in the journal Nature Precision Oncology, Ahlquist argues that a universal screening test…

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Ron Winslow
OneZero

Medical and science journalist now living in Mount Washington Valley, NH, after 33+ year-career as a reporter and editor at The Wall Street Journal.