Neoadjuvant CAPEOX Versus Upfront Surgery for Locally Advanced Colon Cancer With Elevated CEA: A Single-Center, Open-Label, Randomized Controlled Trial

Inclusion Criteria:

Participants must meet all of the following criteria:

Age 18 to 70 years (inclusive) at the time of written informed consent. ECOG performance status 0-1, without deterioration within 2 weeks prior to enrollment; anticipated life expectancy ≥12 weeks.

Histologically or cytologically confirmed colon adenocarcinoma, non-MSI-H/dMMR, with pathologic stage (AJCC/UICC TNM 8th edition) of:

High-risk stage II, or Stage III. High-risk stage II features include: T4, poor/undifferentiated histology (high grade; excluding MSI-H), lymphovascular invasion, perineural invasion, preoperative bowel obstruction or tumor perforation, positive/unknown margin status, insufficient margin clearance, \<12 lymph nodes examined, or high-grade tumor budding.

Tumor location consistent with colon cancer: distal tumor margin ≥12 cm from the anal verge on preoperative endoscopy.

Baseline serum CEA \>5 ng/mL prior to treatment. No evidence of distant metastasis (distant organ and/or distant lymph node metastasis) based on comprehensive clinical evaluation.

Ability to provide required clinical data for study collection. Ability to provide adequate fresh tumor tissue from endoscopy and/or surgery for WES/NGS to develop an individualized ctDNA MRD panel, and ability to provide required blood samples for ctDNA testing (baseline, postoperative \~day 7, postoperative \~day 30).

Candidate for curative-intent R0 resection. Willing and able to comply with the protocol schedule, including regular follow-up visits and necessary treatments, and provides written informed consent.

Exclusion Criteria:

Participants will be excluded if any of the following apply:

Prior or concurrent other malignant tumor. Any severe comorbidity that, in the investigator's judgment, may significantly affect follow-up or short-term survival.

Any other medical condition, or social/psychological circumstance, that in the investigator's judgment makes the participant unsuitable for the study.

MSI-H/dMMR tumor. Evidence of metastatic disease by pathology, clinical assessment, or imaging, including isolated distant lesions, distant disease, or non-contiguous intraperitoneal metastasis.

Multiple primary colon cancers. Underwent open surgery at a non-colon site within 14 days prior to enrollment. Unable to provide required tumor tissue for WES/NGS or personalized MRD panel development, personalized MRD panel customization failure, or unable to provide required blood samples (baseline, postoperative \~day 7, postoperative \~day 30).

History of blood transfusion within 2 weeks prior to surgery or intraoperatively.

Unable to undergo contrast-enhanced CT or MRI for routine clinical follow-up. Fever ≥38°C within the past 7 days, or clinically significant active infection (including active tuberculosis), or active fungal/bacterial/viral infection requiring systemic therapy.

Inadequate bone marrow reserve or organ function meeting any of the following laboratory abnormalities (within 1 week prior to testing without corrective treatment):

ANC \< 1.5 × 10⁹/L Platelets \< 90 × 10⁹/L Hemoglobin \< 90 g/L (\<9 g/dL) ALT \> 3 × ULN AST \> 3 × ULN or total bilirubin \> 1.5 × ULN Creatinine \> 1.5 × ULN or creatinine clearance \< 45 mL/min (Cockcroft-Gault) Albumin \< 28 g/L Pregnant or breastfeeding, or planning pregnancy during the study period. Any other condition that, in the investigator's judgment, indicates the participant should not participate.