Interleukin-6 as a Predictive Marker for Lymph Node and Distant Metastasis in Colorectal Cancer: A Retrospective Cohort Study

Metastasis is the leading cause of death in colorectal cancer (CRC). While interleukin-6 (IL-6), a key inflammatory cytokine, is implicated in tumor metastasis, its specific association with lymph node metastasis (LNM) and distant metastasis (DM) in CRC remains unclear. We retrospectively analyzed clinical data and serum levels of carcinoembryonic antigen (CEA) and cytokines (including IL-6) in 427 CRC patients, stratified by metastatic status. Statistical analyses assessed the predictive value of IL-6 for metastasis. Elevated serum IL-6 levels were significantly associated with both LNM and DM (P<0.05). IL-6 positively correlated with CEA levels (Spearman correlation). Although IL-6 alone showed modest predictive power for LNM (AUC=0.555), it outperformed CEA (AUC=0.525). Combining IL-6 and CEA improved diagnostic accuracy for LNM (AUC=0.583). Notably, IL-6 demonstrated greater sensitivity than CEA in predicting DM (77.30% vs 67.40% at optimal cutoff). These findings demonstrate that IL-6 holds significant predictive value for metastasis in CRC, particularly excelling in the prediction of LNM. The detection of IL-6 offers a valuable complementary approach to the existing clinical prediction paradigm for CRC metastasis risk.