Lateral lymph node dissection after neoadjuvant (chemo)radiotherapy may improve oncological outcomes in Western patients with low rectal cancer.

Abstract

163 Background: In the West, rectal cancer patients with pre-treatment abnormal lateral lymph nodes (LLN) are commonly treated with neoadjuvant (chemo)radiotherapy (n(C)RT) followed by total mesorectal excision (TME). Few centers perform lateral lymph node dissection (LLND) in addition to this, with the aim of improving oncological outcomes. To date, no comparative data are available in Western patients. Methods: An international multi-center cohort study was conducted comparing six centers from the Netherlands and Australia treating patients with abnormal LLN (≥5mm short-axis) with n(C)RT and TME (LLND- group) versus similarly staged patients from a dedicated cancer center in the USA who underwent a LLND in addition to n(C)RT and TME (LLND+ group). Results: Data were available on 169 patients. LLND+ patients (n = 44) consisted of significantly younger and more female patients with higher ASA-scores and ypN-stages compared to LLND- patients (n = 115). LLND+ patients also had a larger median LLN short-axis and were more likely to receive adjuvant chemotherapy (100 vs. 30%; p < 0.0001). Between groups, the lateral local recurrence rate (LLRR) was 0% for LLND+ vs. 7% for LLND- (p = 0.09) and the local recurrence rate (LRR) was 3% for LLND+ vs. 11% for LLND- (p = 0.13). No significant differences were observed in disease-free survival (DFS, p = 0.94) or overall survival (OS, p = 0.42). Sub-analysis of patients who underwent adjuvant chemotherapy (LLND- patients: n = 35) demonstrated clinically relevant though non-statistically significant trends towards a lower LLRR (0% for LLND+ vs. 6% for LLND-; p = 0.07), LRR (3% for LLND+ vs. 14% for LLND-; p = 0.06), DFS (p = 0.19) and OS (p = 0.17) in favour of the LLND+ group. Conclusions: Lateral lymph node dissection in addition to neoadjuvant (chemo)radiotherapy may improve oncological outcomes in Western patients with low rectal cancer and abnormal lateral lymph nodes.