Surgical and oncologic outcomes of cT4b rectal cancer: a propensity score-matched comparison between a university center and regional hospitals.

PURPOSE: Surgery for cT4b rectal cancer remains technically demanding, and outcomes may vary substantially across institutions. This study evaluated perioperative and oncologic outcomes of cT4b rectal cancer surgery performed at a university center compared with those at regional hospitals within a collaborative network. METHODS: A total of 103 patients who underwent curative-intent surgery for cT4b rectal cancer between 2016 and 2024 were retrospectively reviewed. After 1:1 propensity score matching based on baseline characteristics and treatment factors, 54 patients were included in the analysis. Perioperative outcomes, pathological findings, and long-term oncologic outcomes were compared between the university hospital and affiliated regional institutions. Overall survival, relapse-free survival, and local control rate were additionally evaluated in patients with pathological stage II-III disease. RESULTS: Postoperative hospital stay was significantly shorter at the university center (18 days vs. 25 days, P=0.022). Local control was higher in the university hospital group (3-year local control rate: 95.2% vs. 71.5%, P=0.025). Among patients with pathological stage II-III disease, 3-year relapse-free survival was comparable between groups (51.8% vs. 49.0%, P=0.434), whereas local control demonstrated a favorable trend in the university hospital group (91.7% vs. 65.4%, P=0.063). CONCLUSION: Perioperative safety in cT4b rectal cancer surgery was comparable across institutions; however, higher local control at the university center suggests that technically complex cases may benefit from selective centralization in specialized centers. These findings support a hybrid model in which regional collaboration ensures safety while advanced procedures are concentrated in specialized centers.