High IDO-1 expression in tumor endothelial cells is associated with response to immunotherapy in metastatic renal cell carcinoma.

Nivolumab belongs to the standard therapy in the second-line setting of metastatic renal cell carcinoma (mRCC). Although deep and long-lasting responses are seen in some patients, the majority of patients will further progress. PD-L1 is still under critical evaluation as a predictive biomarker.