Prognostic value of residual lymph node status in patients with pathological T0 rectal cancer after neoadjuvant therapy

Background: A yield pathological T0 (ypT0) classification usually indicates the pathologically complete response of rectal cancer to neoadjuvant therapy. However, lymph node metastasis may still be present. Objectives: In this study, we aimed to evaluate the prognostic value of residual lymph node status in patients with pathological T0 rectal cancer after neoadjuvant therapy. Design: Retrospective cohort study. Methods: Patients with locally advanced rectal cancer (LARC) who had undergone preoperative therapy and were pathologically classified as having ypT0 disease at Fudan University Shanghai Cancer Center between December 2012 and September 2022 were retrospectively analyzed. Uni- and multivariate analyses were performed to evaluate the effect of the residual lymph node status on disease-free survival (DFS) and overall survival (OS). Results: A total of 457 patients had ypT0 disease; this included 413 patients with ypT0N0 and 44 with ypT0N1-2. Inadequate lymph node retrieval (<12, p = 0.002) and adenocarcinoma (p = 0.009) were more common in the ypT0N0 group than in the ypT0N1-2 group. The ypT0N1-2 group showed marginal evidence of a higher probability of elevated pretreatment carcinoembryonic antigen levels and adjuvant chemotherapy than the ypT0N0 group (p = 0.076 and p = 0.077, respectively). Patients with ypT0N0 had significantly better 5-year DFS than those with ypT0N1-2 (84.8% vs 68.4%, p = 0.016). However, no significant difference was observed in the 5-year OS between the two groups (93.9% vs 88.8%, p = 0.602). Multivariate analysis revealed that residual lymph node status was an independent prognostic factor for DFS (hazard ratio, 2.285; 95% confidence interval: 1.246-4.192, p = 0.008). Conclusion: Residual lymph node metastasis may affect DFS, but not OS, in pathological T0 patients who receive neoadjuvant therapy followed by radical surgery for LARC.