Local Excision Versus Transanal Multipoint Full-Layer Puncture Biopsy for Patients with Ultra-Low Rectal Cancer with Clinical Complete Response or Near-Complete Response After Neoadjuvant Therapy: a Prospective, Multicenter, Randomized Controlled Clinical Trial

INTERVENTION: Control group:Local excision;Experimental group:Transanal multi‐point full‐thickness punch biopsy; CONDITION: Ultra‐low rectal cancer PRIMARY OUTCOME: Organ Preservation Rate; SECONDARY OUTCOME: Stoma‐Free Survival;Non‐Regrowth Disease‐Free Survival;Adverse Event; INCLUSION CRITERIA: 1. 18–70 years old; 2. Histologically confirmed rectal adenocarcinoma (mucinous adenocarcinoma and signet‐ring cell carcinoma excluded); 3. Tumor lower edge <= 4 cm from the anal verge as confirmed by initial pelvic MRI; 4. T3–4 or N+M0; MRF (+/‐); EMVI (+/‐); 5. Achieved clinical complete response (cCR) or near‐complete response (near‐cCR) after neoadjuvant therapy, and opted for local excision or transanal multi‐point full‐thickness punch biopsy; 6. Negative lateral lymph nodes; 7. Basal maximum diameter = 5 cm or circumferential extent of invasion = 2/3 of the bowel circumference on initial MRI; 8. ECOG performance status 0–1; 9. No evidence of distant metastasis (M0); 10. No systemic infection requiring antibiotic treatment; 11. No prior history of rectal cancer surgery; 12. Patient has read and signed the informed consent form and agreed to participate in this study.