CtDNA Shows Promise for Detecting Molecular Residual Disease in Stage II/III Colorectal Cancer: BESPOKE CRC Final Analysis

The final analysis of the BESPOKE CRC study, presented at the 2025 ASCO Gastrointestinal Cancers Symposium by Purvi Shah, MD, of Virginia Cancer Institute, sheds light on the utility of circulating tumor DNA (ctDNA) testing in detecting molecular residual disease (MRD) in patients with stage II and III colorectal cancer (CRC). This prospective, multicenter, observational study underscores the prognostic significance of ctDNA positivity and its potential role in guiding treatment decisions and improving disease-free survival (DFS).

Study Design and Objectives

The BESPOKE CRC study included 1,001 patients with stage II or III CRC who underwent surgical resection. Patients were monitored using a personalized, tumor-informed, 16-plex multiplex polymerase chain reaction–next generation sequencing ctDNA assay (Signatera, Natera, Inc) to evaluate MRD and recurrence. Plasma samples were collected at multiple time points—2 to 12 weeks after surgery and after adjuvant chemotherapy (ACT)—to assess ctDNA positivity, DFS, and patient outcomes.

Key endpoints of the study included the impact of ctDNA testing on treatment decisions, rates of asymptomatic recurrence, MRD clearance, survival of patients without MRD, and overall survival.

Results

Among the study cohort, 62.4% of patients received ACT; 25.9% of patients with stage II and 91.3% of patients with stage III CRC opted for this treatment. A significant association between ctDNA positivity and inferior DFS was observed during both the MRD and surveillance windows, providing critical insights into recurrence risk.

During the MRD window, ctDNA positivity was detected in 8.1% of patients with stage II and 24.9% of those with stage III CRC.

Patients who had ctDNA-positive results had significantly worse DFS compared with those who had ctDNA-negative results:

• Stage II: Hazard ratio (HR) = 10.4; P<.0001
• Stage III: HR = 10.1; P<.0001

The 18-month DFS estimates for patients with stages II and III CRC combined were significantly different:

• Patients without MRD: 93%
• Patients with MRD: 44.4%

Similar trends were observed during the surveillance period. In the observation cohort, 6.8% of patients with stage II and 33.3% of those with stage III CRC had ctDNA-positive results, with significantly worse DFS (stage II: HR, 34.9; P<.0001; stage III: HR, 34.1; P=.0008).

In the ACT-treated cohort, 10.9% of patients with stage II and 21.1% of those with stage III CRC became ctDNA positive, correlating with significantly reduced DFS (stage II: HR,  131.4; P<.0001; stage III: HR, 54.6; P<.0001).

Implications for Practice

The study highlights ctDNA’s prognostic power in detecting MRD and predicting recurrence risk for patients with CRC. Circulating tumor DNA positivity strongly correlated with inferior DFS, offering a valuable tool for risk stratification and treatment optimization. For patients with ctDNA-positive results after surgery or ACT, enhanced surveillance or more aggressive therapeutic strategies may be warranted. The BESPOKE CRC findings underscore the need for further research into ctDNA-guided treatment strategies.