One proof-of-concept study, for example, presented by researchers at the American Society of Clinical Oncology (ASCO) Annual Meeting in June, found that, among 124 patients with advanced lung, breast, or prostate cancer, in 89% of cases where at least 1 genetic change was found, the genetic change was also detected in the patient’s DNA blood fragments.3

At Stanford, Dr Diehn said, investigators also have an interest in the liquid biopsy’s role in earlier disease, with ongoing clinical studies evaluating whether measuring circulating tumor DNA in localized lung cancers allows detection of microscopic disease after radiation and surgery.

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“Some patients will develop residual microscopic disease, but a significant fraction can be cured after we’ve completed local treatments,” he said. “We want to see if the cancer will come back.”

Amid the excitement, however, come several cautionary notes.

“Maybe, the right question is not so much whether a single mutation might be helpful,” Dr Davidson said. “What we really need to know is which mutations are actionable, or treatable, in a way that helps patients.”

Dr Lichtenfeld agreed. “We don’t want to repeat the PSA [prostate-specific antigen] debacle,” he said, referring to the test heavily promoted for years as an early screening method for prostate cancer, leading in some cases to unnecessary treatment for indolent disease.

Dr Lichtenfeld calls that experience an “instructive reminder” not to rush the science before all the clinical evidence is in. While liquid biopsies could prove successful in monitoring treatments, these tests also might find early-stage cancers that, left alone, might never progress.

A recent study in JAMA found that at least 15% of women with breast cancers characterized as “ultra-low risk” on a molecular signature test after surgery had “exceedingly low” risk for recurrence or death after 20 years. The secondary analysis identified being ultra-low risk as the most significant predictor of a good outcome.4

“Just because we can do something does not mean we should,” Dr Lichtenfeld said. “We still need to know how often to do these tests, what the cost is, and whether they make a difference to patients.”


  1. Perakis S, Speicher MR. Emerging concepts in liquid biopsies. BMC Med. 2017;15(1):75. doi: 10.1186/s12916-017-0840-6
  2. FDA approves first blood test to detect gene mutation associated with non-small cell lung cancer. US Food and Drug Administration website. newsroom/pressannouncements/ucm504488.htm. Published June 1, 2016. Accessed August 2017.
  3. Grail passes early test in quest to find cancer in blood. Reuters website. Published June 3, 2017. Accessed August 2, 2017.
  4. Esserman LJ, Yau C, Thompson CK, et al. Use of molecular tools to identify patients with indolent breast cancers with ultralow risk over 2 decades. JAMA Oncol. 2017 Jun 29. doi: 10.1001/jamaoncol.2017.1261 [Epub ahead of print]