The assay is used in the United States for surveillance of resected CRC "despite limited data supporting such practice," Dr. Marwan Fakih, co-director of gastrointestinal cancer program at City of Hope, in Duarte, California, and colleagues note in JAMA Network Open.
In a study of 48 patients with resected CRC, the researchers sough to determine whether serial ctDNA analysis is more sensitive and leads to earlier detection of cancer recurrence compared with standard imaging and evaluation of CEA levels per National Comprehensive Cancer Network (NCCN) guidelines.
They found that 15 patients experienced CRC recurrence, of whom only eight had a concurrent positive ctDNA finding.
The combination of imaging and CEA measurement was numerically more sensitive than ctDNA in identifying disease recurrence (73.3% vs. 53.3%, P=0.55), the researchers report.
"Imaging remains the most important surveillance assay in the follow-up of resected colorectal cancers," Dr. Fakih said in a news release.
"Clinicians should continue to abide by NCCN guidelines. For those who decide to implement ctDNA into their surveillance algorithm, they should be aware of the limitations associated with this assay," Dr. Fakih said.
It may be premature to base treatment decisions solely on ctDNA results "given the limitations of Signatera sensitivity," he added.
"For now, ctDNA can be considered, if any at all, as a complement to the standard approach recommended by the NCCN, but one must be cognizant of its limitations," Dr. Fakih advised.
The author of a linked editorial notes that the Signatera ctDNA assay detects molecular residual disease (MRD) in a variety of solid cancers, including colorectal cancer.
Results of this small study are "by no means definitive regarding the capability of the Signatera assay's ability to find MRD in patients with colorectal cancer," writes Dr. Alan Venook of the Helen Diller Family Comprehensive Cancer Center at the University of California, San Francisco.
"Mature data from rigorous clinical trials, such as the BESPOKE study currently under the sponsorship of Natera, are needed to settle the issue of the role of ctDNA in colorectal cancer surveillance," Dr. Venook adds.
"If ctDNA can indeed detect MRD sooner than imaging, then interventional trials with molecular response as an end point are warranted to determine whether ctDNA detection is an actionable finding or merely advanced notice that the cancer is destined to recur," he says.
In email to Reuters Health, a spokesperson for Natera said, "We are proud of the performance of Signatera, which has demonstrated high sensitivity and specificity in over a dozen peer-reviewed studies, with over 3,000 patients studied across multiple cancer types, including in large multi-center trials like CIRCULATE."
"While we welcome independent clinical research, small clinical experience studies are subject to limitations and variability. Natera has always supported the use of Signatera in combination with imaging, to inform treatment decisions and detect recurrence as early as possible in patients with a history of cancer."
The study had no specific funding.
SOURCE: https://bit.ly/3pKrgFh and https://bit.ly/3sTu2u1 JAMA Network Open, online March 8, 2022.
By Megan Brooks
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