The Impact of Lymph Node Harvest on Recurrence in Rectal Cancer Following Neoadjuvant Chemoradiotherapy.

BACKGROUND: While current guidelines recommend harvesting ≥ 12 lymph nodes (LNs) for rectal cancer staging, its appropriateness after neoadjuvant chemoradiotherapy (nCRT) remains debated. This study evaluated the prognostic value of harvested lymph nodes (HLNs) following nCRT. METHODS: We retrospectively analyzed 1,596 patients who underwent radical surgery for rectal cancer following nCRT at two tertiary hospitals between April 2004 and December 2021. Patients were categorized by the number of HLNs (≥ 12 vs. <12). Clinicopathologic outcomes and recurrence were compared, and multivariable analyses were performed to identify factors associated with recurrence and survival. RESULTS: HLNs < 12 were found in 321 patients (20.1%), and ≥ 12 in 1,275 (79.9%). No significant differences were observed in age, sex, tumor height, resection margins, or circumferential resection margin involvement. The HLNs ≥ 12 group showed more advanced ypT, ypN, and overall stage, with higher rates of venous and perineural invasion. Completeness of postoperative chemotherapy was comparable. However, the HLNs < 12 group demonstrated a higher recurrence rate (24.6% vs. 18.8%, p = 0.026). In multivariate analysis, HLNs < 12 were identified as independent risk factors for overall survival (HR = 1.624, p = 0.002) and disease-free survival (HR = 1.297, p = 0.047). Kaplan-Meier analysis showed 5-year overall survival was significantly lower in the HLNs <12 group than the HLNs ≥12 group (83.1% vs. 86.1%, p = 0.003). CONCLUSION: Harvesting fewer than 12 LNs was significantly associated with worse overall survival and remains an independent prognostic factor of rectal cancer following nCRT.