Minimal Residual Disease Detection using a Plasma-only Circulating Tumor DNA Assay in Patients with Colorectal Cancer

Clin Cancer Res. 2021 Oct 15;27(20):5586-5594. doi: 10.1158/1078-0432.CCR-21-0410. Epub 2021 Apr 29.


Purpose: Detection of persistent circulating tumor DNA (ctDNA) after curative-intent surgery can identify patients with minimal residual disease (MRD) who will ultimately recur. Most ctDNA MRD assays require tumor sequencing to identify tumor-derived mutations to facilitate ctDNA detection, requiring tumor and blood. We evaluated a plasma-only ctDNA assay integrating genomic and epigenomic cancer signatures to enable tumor-uninformed MRD detection.

Experimental design: A total of 252 prospective serial plasma specimens from 103 patients with colorectal cancer undergoing curative-intent surgery were analyzed and correlated with recurrence.

Results: Of 103 patients, 84 [stage I (9.5%), II (23.8%), III (47.6%), IV (19%)] had evaluable plasma drawn after completion of definitive therapy, defined as surgery only (n = 39) or completion of adjuvant therapy (n = 45). In "landmark" plasma drawn 1-month (median, 31.5 days) after definitive therapy and >1 year follow-up, 15 patients had detectable ctDNA, and all 15 recurred [positive predictive value (PPV), 100%; HR, 11.28 (P < 0.0001)]. Of 49 patients without detectable ctDNA at the landmark timepoint, 12 (24.5%) recurred. Landmark recurrence sensitivity and specificity were 55.6% and 100%. Incorporating serial longitudinal and surveillance (drawn within 4 months of recurrence) samples, sensitivity improved to 69% and 91%. Integrating epigenomic signatures increased sensitivity by 25%-36% versus genomic alterations alone. Notably, standard serum carcinoembryonic antigen levels did not predict recurrence [HR, 1.84 (P = 0.18); PPV = 53.9%].

Conclusions: Plasma-only MRD detection demonstrated favorable sensitivity and specificity for recurrence, comparable with tumor-informed approaches. Integrating analysis of epigenomic and genomic alterations enhanced sensitivity. These findings support the potential clinical utility of plasma-only ctDNA MRD detection.See related commentary by Bent and Kopetz, p. 5449.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Circulating Tumor DNA / blood*
  • Colorectal Neoplasms / blood*
  • Colorectal Neoplasms / pathology
  • Colorectal Neoplasms / surgery*
  • Female
  • Hematologic Tests
  • Humans
  • Male
  • Middle Aged
  • Neoplasm, Residual / blood*
  • Prospective Studies


  • Circulating Tumor DNA