Predictive Role of Circulating Tumor DNA in Stage III Colon Cancer Treated With Celecoxib: A Post Hoc Analysis of the CALGB (Alliance)/SWOG 80702 Phase 3 Randomized Clinical Trial.

Importance: Observational studies have associated use of aspirin and selective cyclooxygenase inhibitors with decreased recurrence and improved survival in patients with colon cancer. While randomized clinical trials have not shown benefit across all patients, these findings suggest that select subgroups may benefit from their use. Despite the well-established prognostic value of circulating tumor DNA (ctDNA), its role in guiding treatment remains unclear. Objective: To investigate the predictive value of postoperative ctDNA for survival outcomes with adjuvant celecoxib alongside conventional chemotherapy in patients with stage III colon cancer. Design, Setting, and Participants: This was a post hoc analysis of the phase 3 Cancer and Leukemia Group B (now Alliance)/Southwest Oncology Group 80702 randomized clinical trial (2010-2015) assessing adjuvant celecoxib vs placebo and 3 vs 6 months of adjuvant 5-fluorouracil, leucovorin, and oxaliplatin for stage III colon cancer. Patients consented to biospecimen collection and had ctDNA analysis performed. Data analysis was performed from September 2024 to June 2025. Exposures: Postoperative ctDNA positivity was determined using a clinically validated, tumor-informed 16-plex-polymerase chain reaction-next-generation sequencing assay (Signatera; Natera Inc) performed between surgery and initiation of adjuvant therapy. Main Outcomes and Measures: Disease-free survival (DFS) and overall survival (OS). Survival by ctDNA status and adjuvant celecoxib use were assessed as part of a post hoc companion study with prespecified statistical analysis plan. Results: Among 940 patients (mean [SD] age, 60.9 [10.8] years; 426 female [45.3%] and 515 male [54.7%] individuals; 222 [23.6%] with prior low-dose aspirin use; and median follow-up of 6.0 [95% CI, 6.0-6.0] years), 767 (81.6%) were ctDNA negative and 173 (18.4%) were ctDNA positive. ctDNA positivity was highly prognostic of worse DFS (reference, ctDNA negativity; adjusted hazard ratio [aHR], 6.12; 95% CI, 4.66-8.03) and OS (aHR, 5.86; 95% CI, 4.19-8.19). In patients with ctDNA positivity, celecoxib was associated with improved DFS (aHR, 0.61; 95% CI, 0.42-0.89) and OS (aHR, 0.62; 95% CI, 0.40-0.96) compared to placebo. Among patients with ctDNA negativity, celecoxib did not provide survival benefit (DFS: aHR, 0.76; 95% CI, 0.53-1.09; OS: aHR, 0.85; 95% CI, 0.54-1.36), although the interaction was not significant (P for interaction, .41 and .33 for DFS and OS, respectively). These findings persisted when stratifying patients by microsatellite instability status and PIK3CA mutational status. Conclusion and Relevance: The findings of this post hoc analysis suggest that ctDNA status has the potential to inform clinical decision-making among patients with stage III colon cancer who should consider adjuvant celecoxib in addition to conventional chemotherapy. Trial Registration: ClinicalTrials.gov Identifier: NCT01150045.