Prognostic impact of residual lateral lymph node metastasis after neoadjuvant (chemo)radiotherapy in patients with advanced low rectal cancer

Background: There is a lack of large studies focusing on the prognostic significance of lateral lymph node (LLN) metastasis following LLN dissection (LLND) in rectal cancer. The aim of this study was to evaluate the prognostic impact of LLN metastases on survival of patients with advanced low rectal cancer. Methods: Consecutive patients with locally advanced, but not metastatic, extraperitoneal rectal cancer treated with neoadjuvant (chemo)radiotherapy plus total mesorectal excision between 2004 and 2015 were included in the study. LLND was performed when pretreatment imaging documented enlarged LLNs (7mm or greater in size). Localization of nodal metastases and long-term outcomes were analysed. Kaplan- Meier analysis was used to compare the survival of patients with ypN0 disease with that of patients with mesorectal ypN+/LLN- status and patients with positive LLNs. The Cox proportional hazards model was used to evaluate predictors of disease-free survival (DFS) and local recurrence. Results: A total of 613 patients were included in the study; LLND was performed in 212 patients (34.6 per cent) and 57 (9.3 per cent) had LLN metastasis. Patients with LLN metastasis had improved DFS and local recurrence cumulative incidence rates compared with patients with mesorectal ypN2+/LLN-disease (DFS: P = 0.014; local recurrence: P = 0.006). Although the DFS rate of patients with LLN metastasis was worse than that of patients with ypN0 disease (P < 0.001), the cumulative incidence of local recurrence was similar (P = 0.491). In multivariable analysis, residual LLN metastasis was not an independent predictor of worse DFS or local recurrence. Conclusion: LLN metastasis is not an independent predictor of local recurrence or survival. Survival of patients presenting with LLN metastasis after (chemo)radiotherapy was intermediate between that of patients with ypN0 status and those with mesorectal ypN2 positivity.