RecruitingPhase 3Drug trialctDNA-Based Adjuvant Chemotherapy for High-Risk Rectal CancerThe goal of this clinical trial is to investigate whether adjuvant chemotherapy can prevent disease recurrence in patients with high-risk rectal cancer who have detectable ctDNA after surgery. The main research question the REACT study aims to answer is: \- Does adjuvant chemotherapy improve disease-free survival in patients with high-risk rectal cancer with detectable ctDNA after surgery? Interventions: \- Patients with detectable ctDNA after surgery and randomised to the experimental group will be offered adjuvant chemotherapy (4 cycles CAPOX/6 cycles FOLFOX) within 12 weeks after surgery.