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

Background: 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.

Methods: 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.

Results: 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).

Conclusion: 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.