D3 lymph node dissection improves survival in stage IV colorectal cancer：A Propensity Score-Matched Retrospective Study

Background: Optimal surgical treatment of stage IV colorectal cancer (metastatic CRC [mCRC]) remains controversial. The present study was undertaken to investigate the impact of extensive lymph node dissection (LND) in this setting. Methods: This retrospective cohort study analyzed 581 patients with stage IV CRC at a high-volume cancer center in Japan. All received surgical treatment between April 2007 and December 2020. Subjects were stratified by nature of LND (D3 vs non-D3 [nD3]) and then propensity score matched at 1:1 ratio. Overall survival (OS) and Cancer-specific survival (CSS) was analyzed before and after pairing, determining independent risk factors through COX regression. Results: Patients assigned to D3 and nD3 LND groups totaled 389 (67.0%) and 192 (33.0%), respectively. Five-year OS proved superior for the D3 (vs nD3) group, both before (42.0% vs 17.9%; p <0.001) and after (51.0% vs 18.1%; p <0.001) PSM. Lymph Node Metastasis (LNM)also emerged as an independent prognosticator of OS in multivariate analyses conducted before (hazard ratio [HR]=0.44, 95% confidence interval [CI]: 0.34-0.57; p <0.001) and after (HR=0.36, 95% CI: 0.251-0.52; p <0.001) matching. The same was true of 5-year CSS, both before (D3, 43.9%; nD3, 20.2%; p <0.001) and after (D3, 52.8%; nD3, 20.2%; p <0.001) matching, again verifying LNM as an independent prognostic factor before (HR=0.43, 95% CI: 0.33-0.56; p <0.001) and after (HR=0.35, 95% CI: 0.245-0.51; p <0.001) PSM. No significant differences in perioperative complications were observed between groups before or after matching. Conclusions: D3 LND improves the prognosis of patients with stage IV CRC, without triggering undue perioperative complications.