Management of Responsive Lateral Pelvic Nodes After Neoadjuvant Therapy in Rectal Cancer (RESPONDER)

OBJECTIVE: To determine whether lateral pelvic lymph node dissection improves oncological outcomes in patients with rectal cancer with radiologically responsive lateral pelvic nodes (LPNs) following neoadjuvant chemoradiotherapy (nCRT). SUMMARY BACKGROUND DATA: The optimal management of radiologically responsive LPNs after nCRT remains unclear. METHODS: This retrospective cohort study included patients with mid-to-low rectal adenocarcinoma who underwent radical resection between 2012 and 2022 at eight tertiary centers. Eligible patients had baseline magnetic resonance imaging evidence of lateral pelvic node enlargement (short-axis ≥5 mm) that decreased to <5 mm after nCRT. Inverse probability of treatment weighting was used to address selection bias. Weighted Kaplan-Meier and Cox proportional hazards models were used to compare disease-free survival, overall survival, and local recurrence. RESULTS: Of 844 patients, 451 underwent total mesorectal excision alone and 393 underwent total mesorectal excision with LPN dissection. Dissection was associated with longer operative time (279.3 vs. 237.9 min; P<0.001) and higher early complication rates (27.0% vs. 19.6%; P=0.011). The 5-year local recurrence, disease-free survival, and overall survival rates were 3.1% vs. 5.3% (hazard ratio [HR], 0.738; 95% confidence interval [CI], 0.207-2.634; P=0.640), 77.1% vs. 71.4% (HR, 0.80; 95% CI, 0.50-1.29), and 87.0% vs. 86.9% (HR, 0.79; 95% CI, 0.22-2.81) with and without lymph node dissection, respectively. CONCLUSIONS: Among patients with radiologically responsive LPNs after nCRT, omission of lateral pelvic lymph node dissection did not compromise oncological outcomes. These data support a response-based surgical strategy to reduce operative morbidity without affecting recurrence or survival rates.