Plasma and Tissue Inflammatory and Angiogenic Biomarkers to Explore Resistance to EGFR-TKIs and Association with VeriStrat Status: Topic: EGFR Biomarkers

Background VeriStrat is a proteomic test validated to be prognostic and predictive of overall survival (OS) to EGFR Tyrosine Kinase Inhibitors (TKIs) in EGFR wild type patients1. Serum Amyloid A1 (SAA1) and its two truncated forms are responsible for 4 of the 8 peaks overexpressed in Veristrat (VS) Poor classified patients. The aim of the study was to explore if the microenvironment, with its complex network mediated by inflammation and angiogenesis could represent the base of the aggressive disease behavior of VS Poor subjects. Moreover, the activity of the immune escape axis PD-1/PD-L1 was explored. Methods Plasma biomarkers analyses were retrospectively performed on plasma baseline samples of 244 patients enrolled in the PROSE trial1, while exploratory tissue analysis was performed on 37 available histological specimens. Circulating levels of HGF, VEGF, FGF, Cromogranin A (CgA) and its pro- and anti-angiogenic fragments (fragment 1-373 and 1-76, respectively) were determined by an ELISA assay. PD-L1 expression both on tumor cells and inflammatory elements of the tumor microenvironment, and the tissue expression (T) of HGF and its receptor c-MET were measured by immunohistochemistry. Results CgA, HGF, VEGF, and FGF plasma levels were statistically significantly higher in VS Poor subjects. High plasma HGF levels were associated with lower PFS (3.4 versus 2.0 months, HR 1.67; 95% CI 1.25-2.23; p<0.001) and OS (11.2 versus 6.4 months, HR 1.64; 95% CI 1.12-2.23 p=0.002). High PD-L1- tumor expression was associated with worse PFS (5.9 versus 1.9 months, HR 2.28; 95% CI. 1.14-4.57; p<0.020) and a trend for lower OS (14.6 versus 6.7 months, HR 1.47; 95% CI 0.85-2.53; p=0.165), but not significantly associated with VS status (p=0.656). At the multivariate analysis, CgA, HGF and VEGF were independently associated with VS Poor status. When clinical variables were also included (histology and PS), multivariate analysis evidenced VEGF as the only independent biomarker associated with the VS Poor classification (p=0.0013). Plasma HGF levels (HR 2.083; 95% CI. 1.306-3.321; p=0.0021) and tumor PD-L1 expression (HR 2.579; 95% CI 1.036-6.421; p=0.0417) remained independent prognostic biomarkers for shorter PFS. Conclusion Inflammation and angiogenesis appear to be associated with the complex processes at the base of the Veristrat signature. Plasma HGF levels and tumor tissue PD-L1 are prognostic in terms of a worse PFS, but VeriStrat remains the only highly reproducible clinically relevant biomarker associated with OS. 1V Gregorc et al, The Lancet Oncology, p713, 15(7), 2014.