Serum IL-8 level as a candidate prognostic marker of response to anti-angiogenic therapy for metastatic colorectal cancer.

PURPOSE: Liver metastasis (LM) is associated with poor prognosis in patients with metastatic colorectal cancer (mCRC). Here, we investigated the prognostic utility of several serum factors in mCRC patients with or without LM who were treated with anti-angiogenic agents in first-line (FL) or salvage-line (SL) settings. METHODS: A combined cohort of 125 patients was analyzed in this single institute pooled analysis: FL cohort receiving bevacizumab (n = 71) and SL cohort receiving regorafenib (n = 54). Blood samples were obtained at baseline (BL) and during treatment, and serum factors were measured by ELISA. Overall survival (OS) was analyzed using Kaplan-Meier curves, the log-rank test, and Cox proportional hazard regression methods. RESULTS: In univariate analysis of the combined cohort, right-sided CRC, primary unresected tumor, wild-type KRAS, LM, ≥ 2 metastatic sites, and SL were associated with shorter OS; in multivariable analysis, LM and SL remained significant. Serum angiopoietin-2 (Ang-2) levels ≥ 2190.3 pg/ml and interleukin (IL)-8 levels ≥ 15.1 pg/ml at BL were significantly associated with LM. Using these cut-off values, patients with higher Ang-2 or IL-8 levels at BL had shorter OS than those with lower BL levels (Ang-2: hazard ratio [HR] 2.57, 95% confidence interval [CI] 1.47-4.51, P = 0.001; IL-8: HR 4.31, 95%CI 2.11-8.79, P < 0.001). High serum IL-8 level remained a significant predictor of shorter OS in multivariable analysis (HR 3.24, 95%CI 1.47-7.16, P = 0.004). CONCLUSION: Circulating IL-8 and Ang-2 levels are associated with LM in mCRC patients. IL-8 may be a prognostic marker of response to anti-angiogenic therapy, regardless of the treatment timing.