Impact of Positive Lymph Nodes after Systematic Perihilar Lymphadenectomy in Colorectal Liver Metastases

<b>Background:</b> 25 to 50% of patients suffering from colorectal cancer develop liver metastases. The incidence of regional lymph node (LN) metastases within the liver is up to 14%. The need for perihilar lymph node dissection (LND) is still a controversial topic in patients with colorectal liver metastases (CRLM). This study investigates the role of perihilar LND in patients with CRLM. <b>Methods:</b> For this retrospective study, patients undergoing surgery for CRLM at the University Hospital Basel between May 2009 and December 2021 were included. In patients with perihilar LND, LN were stained for CK22 and examined for single tumour cells (<0.2 mm), micro- (0.2-2 mm), and macro-metastases (>2 mm). <b>Results:</b> 112 patients undergoing surgery for CRLM were included. 54 patients underwent LND, 58/112 underwent liver resection only (LR). 3/54 (5.6%) showed perihilar LN metastases in preoperative imaging, and in 10/54 (18.5%), micro-metastases could be proven after CK22 staining. Overall complications were similar in both groups (LND: 46, 85.2%; LR: 48, 79.3%; <i>p</i> = 0.800). The rate of major complications was higher in the LND group (LND: 22, 40.7%; LR: 18, 31%, <i>p</i> = 0.002). Median recurrence-free survival (RFS) (LND: 10 months; LR: 15 months, <i>p</i> = 0.076) and overall survival (OS) were similar (LND: 49 months; LR: 60 months, <i>p</i> = 0.959). <b>Conclusion:</b> Preoperative imaging is not sensitive enough to detect perihilar LN metastases. Perihilar LND enables precise tumour staging by detecting more lymph node metastases, especially through CK22 staining. However, perihilar LND does not influence oncologic outcomes in patients with CRLM.