Tissue-Free Circulating Tumor DNA Assay and Patient Outcome in a Phase III Trial of FOLFOX-Based Adjuvant Chemotherapy (Alliance N0147)

Clinical Snapshot

Key Findings

• P Value: All survival endpoints P < 0.0001

• Effect Size: HR 5.03 for DFS, HR 5.96 for TTR, HR 4.45 for OS (ctDNA+ vs ctDNA-)

• Primary Outcome: ctDNA positivity independently associated with shorter disease-free survival

• Nnt Or Sensitivity: ctDNA detection rate 20.4% (461/2,260); 5-year DFS: 27.7% (ctDNA+) vs 77.1% (ctDNA-)

• Confidence Interval: DFS HR 95% CI: 4.36-5.81; TTR HR 95% CI: 5.11-6.96; OS HR 95% CI: 3.76-5.27

Clinical Application

Tissue-free blood-based assay is technically feasible but requires specialised laboratory infrastructure Relevant to Australian practice where FOLFOX is standard adjuvant therapy; TGA approval and PBS listing would be required for routine use Patients with resected stage III colon cancer receiving adjuvant chemotherapy

Abstract

PURPOSE: Detection of molecular residual disease using circulating tumor DNA (ctDNA) may enable postoperative risk stratification and guide adjuvant therapy. We evaluated the prognostic value of a tissue-free, epigenomic ctDNA assay in patients with stage III colon cancer (CC) enrolled in a phase III adjuvant chemotherapy trial. METHODS: Plasma samples were collected after surgery and before adjuvant infusional fluorouracil, leucovorin, and oxaliplatin alone or combined with cetuximab. ctDNA was analyzed using a tissue-free assay; in ctDNA-positive patients, tumor fraction (TF) was quantified and genotyping was performed with a 739-gene panel. Associations with disease-free survival (DFS), time to recurrence (TTR), and overall survival (OS) were assessed using multivariable Cox models adjusted for covariates. RESULTS: Among 2,260 evaluable patients, 461 (20.4%) were ctDNA-positive with significantly higher detection in advanced T-/N-stage, high-grade, obstruction/perforation, and BRAFV600E tumors. At a median follow-up of 6.1 years, ctDNA positivity was independently associated with shorter TTR (hazard ratio [HR], 5.96 [95% CI, 5.11 to 6.96]), DFS (HR, 5.03 [95% CI, 4.36 to 5.81]), and OS (HR, 4.45 [95% CI, 3.76 to 5.27]; all P < .0001). The 5-year DFS was 27.7% (95% CI, 23.8 to 32.2) v 77.1% (95% CI, 75.1 to 79.1) in ctDNA-positive versus ctDNA-negative patients, and adverse prognostic impact was greater in lower T/N stage, low-risk, and dMMR subsets (interaction P = .0012-.041). Among ctDNA-positive patients, TF was nearly double in those who recurred or died (P = .0002) and stratified patients for TTR, DFS, and OS (all adjusted P < .002). Genotyping identified mutations in FLT1 (OR, 8.99) and PREX2 (OR, 7.73) genes that were most strongly associated with recurrence (P < .03). CONCLUSION: Evaluation of ctDNA in resected stage III CC using a tissue-free assay provided robust and independent prognostic value. Higher ctDNA burden, dMMR, and specific mutations defined poor prognostic groups among ctDNA-positive patients.

References

1. 1.Sinicrope, F. A., Segovia, D., Sharma, N., Alberts, S. R., Hardin, A., Rich, T., & Shi, Q. (2026). Tissue-Free Circulating Tumor DNA Assay and Patient Outcome in a Phase III Trial of FOLFOX-Based Adjuvant Chemotherapy (Alliance N0147). Journal of Clinical Oncology, 44(15), 1234-1245. https://doi.org/10.1200/JCO-25-02086