Evaluation of PD-L1 (E1L3N, 22C3) expression in venous tumor thrombus is superior to its assessment in renal tumor in predicting overall survival in renal cell carcinoma.

Renal cell carcinoma (RCC) frequently invades renal vein forming neoplastic thrombus. The expression of immune checkpoint receptors in RCC was addressed in multiple studies, but little is known about the expression and prognostic significance of programmed death ligand-1 in tumor thrombus. The study aimed to evaluate the expression of PD-L1 within venous tumor thrombus and primary tumor using 2 independent antibody clones (22c3 and E1L3N) and to assess its value in predicting overall survival (OS) in the subgroup of patients with RCC and renal vein thrombus. Eighty-two patients with RCC and venous tumor thrombus that underwent nephrectomy were enrolled. The expression of PD-L1 was assessed utilizing tissue microarrays separately on tumor cells (TCs) and tumor-infiltrating lymphocytes (TILs). The frequency of PD-L1 expression on TCs and TILs varied between tumor and thrombus compartments and was dependent on the antibody clone used. The expression of PD-L1 on TCs and/or TILs was associated with worse OS irrespectively of the antibody and the analyzed compartment. Nevertheless, the best prognostic performance was noted for the combined assessment of PD-L1 expression on TCs and TILs in venous tumor thrombus with the use of 22c3 antibody. The multivariable Cox regression model predicting OS incorporated PD-L1 22c3 in venous tumor thrombus (hazards ratio [HR] = 3.64, 95% confidence interval [CI] = 1.63-8.14, P = 0.002) and nodal status (HR = 2.88, 95% CI = 1.18-7.03, P = 0.02). PD-L1 may become a valuable tool for prognostic purposes in this specific subgroup of patients and be incorporated into the respective models qualifying for adjuvant treatment.

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