Prognostic value of metastatic lymph node regression grade after neoadjuvant chemoradiotherapy in patients with locally advanced rectal cancer

Background The prognostic value of classifying the degree of metastatic lymph node regression grade after neoadjuvant chemoradiotherapy remains unclear. The aim was to assess the prognostic value of lymph node regression grade in patients with rectal cancer treated with chemoradiotherapy. Methods We reviewed a total of 421 patients with rectal cancer who underwent neoadjuvant long-course chemoradiotherapy. All lymph nodes were examined retrospectively for evidence of response to chemoradiotherapy, and lymph node regression grade was scored as lymph node regression grade 0 (normal lymph node), lymph node regression grade 1 (100% fibrosis), lymph node regression grade 2 (< 25% cancer cells), lymph node regression grade 3 (25%–50% cancer cells), lymph node regression grade 4 (50%–75% cancer cells), and lymph node regression grade 5 (> 75% cancer cells). The prognostic importance of lymph node regression grade was evaluated. Results Among 301 ypN0 patients, 27 patients were scored as lymph node regression grade 1. The 5-year recurrence-free survival and local recurrence rates in lymph node regression grade 1 patients were similar to those in lymph node regression grade 0 patients (96.3% versus 88.1% in recurrence-free survival and 0% versus 2.7% in local recurrence); however, among 120 ypN+ (lymph node regression grade 2-5) patients, the 5-year recurrence-free survival and local recurrence rates were poor regardless of the lymph node regression grade score (38.1%–61.1% in recurrence-free survival and 8.4%–14.0% in local recurrence). In the multivariate analysis, an intensified regimen using systemic chemotherapy was independently associated with more lymph node regression grade 1 (P < .001; odds ratio, 6.06; 95% confidence interval, 2.33–16.20) among patients with lymph node regressions grade 1 through 5. Furthermore, in the multivariate analysis, ypT3-4 (hazard ratio, 7.82; 95% confidence interval, 2.80–27.32; P < .001), lymph node regression grade 1 (hazard ratio, 0.048; 95% confidence interval, 0.002–0.27; P < .001), the number of retrieved lymph nodes < 12 (hazard ratio, 5.48; 95% confidence interval, 1.48–16.38; P = .014), and no perioperative chemotherapy (hazard ratio, 3.01; 95% confidence interval, 1.53–5.68; P = .002) were independent predictors of recurrence-free survival. Conclusion Complete lymph node regression after chemoradiotherapy is a strong prognostic factor in rectal cancer.