Postoperative circulating tumor DNA (ctDNA) testing could transform management for rectal cancer patients undergoing surgery.

• 14.2% of patients were ctDNA-positive shortly post-surgery, with a significantly higher recurrence risk (HR: 9.96, p<0.0001).
• ctDNA-positive patients benefited from adjuvant chemotherapy (HR: 0.28, p=0.031), while ctDNA-negative patients did not (HR: 0.59, p=0.211).

Monitoring ctDNA can guide treatment decisions, optimizing outcomes for high-risk patients and avoiding unnecessary therapies for low-risk individuals.

• Recurrence risk escalated for patients whose ctDNA status worsened from negative to positive (HR: 8.22, p=0.0055) and for those consistently positive (HR: 45.48, p<0.0001).