The goal of this interventional clinical trial is to compare the efficacy of neoadjuvant chemotherapy versus upfront surgery in adults aged 18-70 years with stage II (high-risk)-III, non-MSI-H colon adenocarcinoma and elevated baseline CEA (\>5 ng/mL) undergoing curative-intent treatment. This single-center, open-label, randomized controlled study will evaluate 2-year disease-free survival (2y-DFS) as the primary endpoint, with all study-related procedures-including longitudinal ctDNA-based molecular residual disease (MRD) monitoring, Immunoscore assessment, tumor tissue sequencing, and surveillance imaging-provided at no cost to participants. The main questions it aims to answer are:
* Does a treatment strategy involving neoadjuvant CAPOX followed by surgery improve 2y-DFS compared with upfront surgery followed by standard adjuvant chemotherapy? * Do postoperative ctDNA-MRD status and its longitudinal dynamics predict 2y-DFS? * Does combining ctDNA-MRD with Immunoscore enhance prognostic risk stratification for recurrence beyond either biomarker alone?
Participants will:
* Be randomized 1:1 (N=100) to one of two treatment pathways:
* Arm A: Neoadjuvant CAPOX × 4 cycles → curative surgery (R0 planned) → postoperative management per standard practice * Arm B: Upfront curative surgery → postoperative standard adjuvant chemotherapy per guideline → routine surveillance * Undergo baseline assessments prior to treatment initiation, including blood draw, colonoscopy, primary tumor next-generation sequencing (for personalized ctDNA-MRD assay development), and Immunoscore testing-all provided free of charge as part of the study. * Provide postoperative blood samples for ctDNA-MRD testing at approximately postoperative day \~7 and day \~30 (before adjuvant therapy start, if applicable). * During follow-up, provide serial blood samples every 3 months, aligned with routine surveillance visits, for repeat ctDNA-MRD analysis. * Receive standard-of-care postoperative surveillance (including imaging and clinical evaluations) through 2 years, with all study-mandated assessments covered by the trial.
This trial integrates clinical intervention with comprehensive biomarker profiling to determine whether early systemic therapy alters MRD dynamics and improves outcomes in high-risk, CEA-elevated colon cancer.
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