Selective Total Mesorectal Excision Based on Intra-Operative Frozen Section From Local Excision in Rectal Cancer Undergoing Neoadjuvant Chemoradiotherapy

Inclusion Criteria:

1. Pathologically confirmed rectal adenocarcinoma.
2. Neoadjuvant therapy based on radiotherapy; post-radiotherapy evaluation ≥8 weeks later shows near clinical complete response (near-cCR) or partial response (PR) with residual tumor \<2 cm.
3. Tumor distance from the anal verge ≤5 cm.
4. Age 18-75 years.
5. No synchronous multiple primary cancers.
6. No contraindications to pre-operative radiotherapy or chemotherapy.
7. Adequate organ function (cardiac, hepatic, renal, hematologic).
8. Patient or legally authorized representative able to understand the study protocol, willing to participate, and provide written informed consent.

Exclusion Criteria:

1. Age \<18 or \>75 years.
2. Concurrent or previous malignancy within the past 5 years (except adequately treated basal-cell or squamous-cell skin carcinoma or carcinoma in situ of the cervix).
3. Emergency surgery required for bowel obstruction, perforation, or bleeding.
4. Prior colorectal surgery that may compromise intestinal reconstruction.
5. Need for en-bloc multivisceral resection.
6. ASA physical status IV or V.
7. Pregnant or lactating women.
8. a) Women of child-bearing potential with a positive serum pregnancy test at baseline or who have not undergone pregnancy testing; post-menopausal women must have been amenorrheic for ≥12 months.
9. b) Men or women of reproductive potential unwilling to use effective contraception throughout the study period.
10. Severe psychiatric illness precluding informed consent or compliance.
11. Severe COPD, interstitial lung disease, or ischemic heart disease precluding safe surgery.
12. Continuous systemic corticosteroid therapy within 1 month before enrolment.
13. Contraindications to laparoscopic surgery.
14. Patient or legally authorized representative unable to understand the study conditions and objectives.