March 05, 2018
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Evidence does not support use of liquid biopsies to guide cancer treatment

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Little evidence exists to support the use of most circulating tumor DNA assays in either early- or late-stage cancer, according to a newly published review by ASCO and College of American Pathologists summarizing clinical validity and utility.

“This is an area of great interest to both pathologists and oncologists,” Jason D. Merker, MD, PhD, FCAP, co-chair of the joint panel that performed the study, said in a press release. “It’s also an area where we see a lot of commercial advertisement, and a lot of enthusiasm from the public. We thought it was a good time to look at the literature and take an evidence-based approach to various uses for circulating tumor DNA (ctDNA) assays.”

With the help of a medical librarian, the researchers reviewed all literature available — which included 1,338 references — about the use of ctDNA assays for solid tumors. The review included 77 selected articles published between January 2007 and March 2017.

Although some ctDNA assays showed clinical validity and utility for certain advanced cancers, there was “insufficient evidence” to determine whether using the assays could be justified outside of clinical trials.

There also was insufficient support for the use of ctDNA assays in making treatment decisions in early-stage cancer, detecting residual disease or screening for cancer, except for within the context of clinical trials.

The results of ctDNA assays were frequently discordant with biopsies of tumor tissue, prompting Merker and colleagues to suggest that negative ctDNA results should be confirmed by genotyping tumor tissue.

“There is very significant potential for many different applications of ctDNA tests in the future,” Merker said in the release. “However, we need to make sure that we develop the body of evidence as part of clinical trials to support these applications in various tumor types. This is critical to ensure that we are providing the best care for our patients.”

The researchers noted that the increasing use of ctDNA assays in clinical settings demonstrated the “clear demand” to use the assays to guide decision-making.

Daniel F. Hayes

“Like all new things in medicine, the use of ctDNA assays in routine cancer care requires evidence of clinical utility. At present, there is insufficient evidence of clinical validity and utility for the majority of ctDNA assays in advanced cancer, including those that interrogate a panel of genes,” Daniel F. Hayes, MD, FACP, FASCO, a co-author of the review said in the press release. “What is promising is that this area of research is rapidly evolving, so there should be enough evidence soon to formulate evidence-based guidance for a variety of clinical scenarios.” – by Andy Polhamus

Disclosures: Merker reports consulting/advisory roles with Bio-Rad Laboratories, Genoox and Rainbow Genomics, as well as a patent on measurement and monitoring of cell clonality. Please see the full study for all other authors’ relevant financial disclosures.