P302 - Long-term Oncological Outcomes Of T4b Rectal Cancer Patients After Intersphincteric Resection or Abdominoperineal Resection : A Propensity Score Matched Study

Purpose/Background: This study aimed to compare long-term survival outcomes between intersphincteric resection (ISR) and abdominoperineal resection (APR) in rigorously selected patients.

Methods/Interventions: A retrospective propensity score-matched (PSM) analysis was conducted using a prospectively maintained database (2003–2020). Inclusion criteria comprised: MRI-confirmed cT4b tumors involving the anal canal、≥60-month follow-up(if applicable)、after neoadjuvant chemoradiotherapy (NCRT)、Preoperatively metastasis-free and pathologically confirmed adenocarcinoma. After PSM adjustment for covariates (Distance of tumor from the anal verge(cm)、Tumor size(mm)、Tumor position、Pathologic T stage (pT）、Pathologic N stage (pN)、Adjuvant therapy), 61 ISR-APR matched pairs were analyzed. Primary outcome was 5-year overall survival (OS), assessed via Kaplan-Meier and Robust Cox regression.

Results/Outcomes: The matched cohort (n=122) demonstrated balanced baseline characteristics (p>0.05). No significant difference in 5-year OS was observed in both unmatched groups(p=0.056; ISR: 60.9%, APR: 60.7% , HR 0.92, 95% CI 0.81–1.23) and matched groups(p=0.12; ISR: 70.2%, APR: 63.8% , HR 0.89, 95% CI 0.71–1.26). ISR achieved comparable survival while preserving sphincter integrity .Robust Cox regression models in stratification analysis revealed similar overall survival (HR, 0.75–1.57) for ISR compared with APR.

Conclusion/Discussion: ISR provides oncological safety equivalent to APR in selected cT4b rectal cancer patients with anal canal invasion after optimal NCRT response. For further investigation, the efficacy of ISR in survival and preventing both local and distant disease recurrence must be validated through a multi-center prospective randomized trial