Multiplexed tissue protein assay as a predictor of response to targeted therapy in advanced renal cell carcinoma.

4577 Background: A number of prognostic biomarkers have been explored in advanced renal cancer, but to date none have been useful in therapeutic outcome prediction. Methods: Following regulatory approval, formalin-fixed paraffin embedded (FFPE) pre-therapy (sunitinib and/or mTOR inhibitors) tissue samples and clinical data on kidney cancer patients (pts) were obtained. The FFPE tissue was analyzed using layered immunohistochemistry which allows analysis of multiple biomarkers using a single tissue section. Multiplexed panels of protein biomarkers were used to probe tissue sections for proteins along the PI3K/AKT/mTOR and/or the VEGFR/PDGFR signaling pathways. Expression of biomarkers in tumor tissue was scored and predictive scores which correlated with the pt’s clinical outcome status generated. Results: Tissue samples of 51 pts treated with sunitinib (S)were analyzed. A predictive score was generated by combining the scores assigned to VEGFR1 and VEGFR2 and multiplying the sum with the score of VEGFA. A...