Correlation of markers of oxidative damage and circulating IL6 levels with survival following treatment with bevacizumab in metastatic colorectal cancer patients.

Abstract

e21024 Background: Angiogenesis drives cancer growth, tumour progression and metastases. Hypoxic tumours initiate recruitment of their own blood supply and enhance expression of vascular endothelial growth factor (VEGF). Bevacizumab is a recombinant humanised monoclonal anti-VEGF antibody which prevents VEGF binding to its receptors and improves overall survival in metastatic colorectal cancer patients when combined with cytotoxic chemotherapy. Currently, Bevacizumab is indicated as a first line treatment in all metastatic colorectal cancer patients, however only 38-44% of these patients will have a response to treatment. There is no good marker to predict treatment response. The role of inflammation and oxidative damage in driving angiogenesis and clinical response to bevacizumab is poorly understood. The aim of this study was to investigate the levels of oxidative damage and inflammation in the tissue and in the circulation of patients receiving Bevacizumab. Methods: Tissue from 80 patients was constructed into tissue microarrays (TMAs) and screened by immunohistochemistry for the levels of a DNA adduct marker 8oxodG and a lipid peroxidation marker 4HNE in addition to Ki67 status. Serum was screened for 8oxodG, 4HNE and the inflammatory cytokines; IL1β, IL6, IL8, TNFα and pro-angiogenic factors; Ang 2, TGFβ, VEGF using ELISA. Data was correlated with patient survival following Bevacizumab treatment. Results: 8oxodG stromal nuclear positivity significantly correlated with survival following bevacizumab (p=0.035) and this was independent of cell proliferation status. Following multivariate analysis, circulating IL6 levels also significantly correlated with survival following bevacizumab treatment (p=0.01). Using linear regression, circulating levels of 8oxodG correlated with IL6 levels (p=0.016). Circulating Ang 2 levels correlated with IL6 (p=0.006). Conclusions: We have shown for the first time that levels of a DNA adduct marker 8oxodG and circulating levels of IL6 correlate with survival in metastatic patients receiving Bevacizumab.