Purpose: We evaluated the relationship of the pretreatment serum IL-6 levels with the outcome and treatment response in patients with advanced or metastatic colorectal cancer (CRC) who underwent bevacizumab-containing chemotherapy.
Methods: In this retrospective study, the pretreatment serum IL-6 and plasma vascular endothelial growth factor (VEGF) levels were measured in 113 patients with metastatic CRC. The cut-off values for these measurements, as determined by a receiver operating characteristic curve analysis, were 4.3 and 66 pg/mL, respectively. The median follow-up period was 19 months (range 1-40 months). Sixty-three patients had primary cancer, and 38 had a metachronous recurrence. Thirty patients underwent curative resection, and 71 underwent chemotherapy, 53 of whom received bevacizumab-containing chemotherapy. Overall survival (OS) and progression-free survival (PFS) were estimated using Kaplan-Meier and multivariate Cox proportional hazards regression analyses.
Results: The plasma VEGF levels and positive KRAS mutation status were not associated with the outcomes. However, high serum IL-6 levels were significantly associated with poorer OS and PFS in comparison to low serum IL-6 levels. A Cox proportional hazards regression analysis showed that high serum IL-6 levels were an independent risk factor for a poor outcome.
Conclusion: In patients with metastatic CRC, high pretreatment serum IL-6 levels were associated with a poor outcome and bevacizumab resistance.
Keywords: Bevacizumab; Chemo-resistance; Colorectal cancer; Interleukin-6 (IL-6).