Earlier postoperative ctDNA detection predicts recurrence and adjuvant therapy benefit in stage II-III colorectal cancer

Detection of postoperative minimal residual disease (MRD) using circulating tumor DNA (ctDNA) accurately predicts cancer recurrence and may even guide adjuvant chemotherapy. Cost-effective and easily implementable assays capable of detecting MRD early (within days after surgery) will drive wider clinical adaptation. We developed a rapid, single-tube multiplex quantitative methylation-specific PCR (mqMSP) assay targeting 10 rigorously screened methylation markers. In a preoperative cohort, mqMSP achieved 100% specificity in 96 controls, with an overall sensitivity of 73.1% for CRC. In a postoperative cohort of 246 stage II-III CRC patients with a long follow-up time (7-96 months, median: 48 months), we demonstrated that ctDNA detection by mqMSP at an early timepoint (median: 5 days after surgery) predicted worse disease-free survival (HR 7.43, P < 0.0001) and overall survival (HR 8.81, P < 0.0001). Benefit from completion of recommended adjuvant therapy was only seen for ctDNA-positive patients, but not for ctDNA-negative patients.