Safety and Efficacy of Organ Preservation Treatment for Stage I Rectal Cancer: Optimization of Consolidation Chemotherapy Before Local Excision After Neoadjuvant Chemoradiotherapy (OPTION); A Multi-center, Prospective, Randomized Trial

The goal of this clinical trial is to find out if adding consolidation chemotherapy with capecitabine after total neoadjuvant chemoradiotherapy (TNT) works to improve oncologic outcomes in patients with stage I rectal cancer. It will also comparethe safety of adding consolidation chemotherapy before local excision.

The main questions it aims to answer are:

• Does adding consolidation chemotherapy increase the rate of pathologic complete response?
• What medical problems or side effects do participants have during and after treatment?

Researchers will compare TNT followed by local excision to TNT followed by consolidation chemotherapy with capecitabine and then local excision to see if adding consolidation chemotherapy improves tumor response and treatment outcomes.

Participants will:

• Receive TNT for stage I rectal cancer
• Be randomly assigned to one of two treatment groups
• Undergo local excision after preoperative treatment
• Visit the clinic for checkups and tests to evaluate tumor response, side effects, recurrence, survival, quality of life, bowel function, urinary function, sexual function, circulating tumor DNA, and treatment-related costs

Inclusion Criteria:

• Histologically confirmed rectall adenocarcinoma
• Low rectal cancer (AV < 15cm)
• cT2N0 disease, or pathologic stage T1N0 disease after endoscopic resection with at least one high-risk feature, including: Positive resection margin Lymphovascular invasion Tumor budding ≥5
• Ability to understand and comply with the requirements of the clinical trial

Exclusion Criteria:

• Patients who prefer radical rectal resection
• Prior history of surgery for rectal cancer
• Recurrent rectal cancer
• Synchronous metastatic rectal cancer
• Evidence of lymph node metastasis or distant metastasis on abdominopelvic CT or chest CT, including para-aortic, common iliac, or external iliac lymph node metastasis
• Uncontrolled active infection or other uncontrolled medical condition
• Known hypersensitivity to chemotherapy
• Patients considered unsuitable for participation in the clinical trial by the principal investigator or study personnel