Circulating Tumor DNA Analysis: ASCO and CAP Joint Review

As reported in the Journal of Clinical Oncology and the Archives of Pathology & Laboratory Medicine by Jason D. Merker, MD, PhD, of Stanford University School of Medicine, and colleagues, ASCO and the College of American Pathologists (CAP) have issued a joint review on the status of circulating tumor DNA (ctDNA) testing in patients with solid tumors. The review was motivated by recognition that clinical use of analytic tests to assess genomic variants in ctDNA is increasing and that guidelines for use will be required in the near future. The review was informed by an expert panel literature review on the use of ctDNA assays for solid tumors, including preanalytic variables; analytic validity; interpretation and reporting; and clinical validity and utility. The panel was co-chaired by Dr. Merker (CAP representative) and by Nicholas C. Turner, MD, PhD (ASCO representative), of the Royal Marsden Hospital and the Institute of Cancer Research.

Key Elements

Key elements of the review are summarized/reproduced here:

  • The evidence indicates that testing for ctDNA is optimally performed on plasma collected in cell stabilization or EDTA (ethylenediaminetetra-acetic acid) tubes, with EDTA tubes processed within 6 hours of collection.
  • Some ctDNA assays have demonstrated clinical validity and utility with certain types of advanced cancer; however, there is insufficient evidence of clinical validity and utility for the majority of ctDNA assays in advanced cancer.
  • Evidence shows discordance between the results of ctDNA assays and genotyping tumor specimens and supports tumor tissue genotyping to confirm undetected results from ctDNA tests.
  • There is no evidence of clinical utility and little evidence of clinical validity of ctDNA assays in early-stage cancer, treatment monitoring, or residual disease detection.
  • There is no evidence of clinical validity and clinical utility to suggest that ctDNA assays are useful for cancer screening, outside of a clinical trial.
  • Given the rapid pace of research, reevaluation of the literature will shortly be required, along with the development of tools and guidance for clinical practice.

Tom Oliver, of ASCO, is the corresponding author of the Journal of Clinical Oncology article. e-mail:

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.




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