Large study finds Guardant Reveal blood test improves detection of recurrence risk in stage 3 colon cancer after surgery

In an advance for precision oncology, the largest published study to date on molecular residual disease (MRD) detection in stage 3 colon cancer has demonstrated the prognostic capabilities of Guardant Health's Reveal blood test. Published in January 2026 in Journal of Clinical Oncology, the study analyzed data from the Alliance N0147 phase 3 trial, highlighting how this tissue-free circulating tumor DNA (ctDNA) assay can stratify patients by recurrence risk post-surgery and adjuvant chemotherapy. The blood test identified over 2,000 patients with detectable ctDNA post-surgery who had up to a sixfold higher rate of disease recurrence or reduced survival.

The Alliance N0147 trial was a multicenter phase 3 study, patients with resected stage III colon cancer between 2004 and 2009. Participants were randomized to receive standard adjuvant FOLFOX chemotherapy (leucovorin, fluorouracil, and oxaliplatin) alone or combined with Erbitux (cetuximab). The retrospective analysis involved researchers evaluating postsurgical plasma samples from 2,260 evaluable patients using Guardant Reveal, a sequencing-based assay that detects ctDNA through epigenomic signatures without requiring tumor tissue sequencing. This "tissue-free" approach makes it particularly accessible for real-world clinical settings, where tissue availability can be a barrier.

Key patient characteristics included a median age of 59 years, with balanced representation across tumor stages (T1-4, N1-2), mismatch repair (MMR) status, and molecular subtypes (e.g., BRAF V600E mutations). The primary endpoints were associations with time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS), assessed at a median follow-up of 6.1 years. ctDNA was measured approximately four to eight weeks after surgery but before or during adjuvant chemotherapy initiation.

Of the 2,260 patients, 461 tested ctDNA-positive post-surgery, indicating detectable MRD. Positivity rates were significantly higher in patients with advanced pathologic features, including higher T stage (T4 vs. T1-3), N stage (N2 vs. N1), high-grade histology, bowel obstruction or perforation, and BRAF V600E mutations. This association highlights the assay's sensitivity in identifying aggressive disease biology.

For TTR, ctDNA-positive patients had a hazard ratio (HR) of 5.96 for shorter TTR compared to ctDNA-negative patients, after adjusting for clinicopathologic factors. The DFR HR was 5.03, with 5-year DFS rates of 27.7% for ctDNA-positive versus 77.1% for ctDNA-negative patients. Lastly, OS ctDNA positivity correlated with an HR of 4.45 for reduced OS.

Patients with lower T/N stages, low-risk features, or deficient MMR (dMMR) tumors showed stronger adverse impacts from ctDNA positivity. These results suggest Guardant Reveal can refine risk stratification beyond standard staging, identifying "high-risk" individuals in otherwise favorable cohorts.

Among ctDNA-positive patients, tumor fraction (TF) levels, quantifying ctDNA burden, further stratified outcomes. Higher TF was nearly double in those who recurred or died, with significant associations for TTR, DFS, and OS.

Importantly, the assay's performance was consistent across treatment arms (FOLFOX ± cetuximab), indicating its independence from specific chemotherapy regimens.

Craig Eagle, M.D., Guardant’s chief medical officer, said in a company news release that “this large study adds to growing evidence that ctDNA testing with Guardant Reveal after surgery helps answer the question patients care about most: Am I really cancer-free?....Personalizing care after surgery is essential as clinicians and patients decide what comes next.”

By identifying the 20% of patients at ultra-high risk of recurrence, the test could potentially enable timely escalation of surveillance or intervention, such as intensified imaging, additional therapies, or clinical trial enrollment, while sparing the majority from overtreatment. The ctDNA-negative patients exhibited excellent 5-year DFS, supporting de-escalation strategies like reduced follow-up intensity. The ctDNA testing for risk stratification in cancer care, particularly colon cancer, could help lower healthcare expenditures.