Immune checkpoint inhibitors are now standard of care for many patients with metastatic renal cell carcinoma (mRCC) and metastatic urothelial carcinoma (mUC). Given real-world limitations in programmed death-ligand 1 (PD-L1) testing, concordance studies between PD-L1 assays are needed. We undertook comparisons of Dako 28-8 and Ventana SP142 assays in mRCC and Dako 22C3 and Ventana SP263 assays in mUC.
Thirty-two patients with mRCC and 18 patients with mUC who had received immune checkpoint inhibitor therapy were identified. Formalin-fixed paraffin-embedded tumor samples for patients with mRCC were evaluated with Dako 28-8 and Ventana SP142 PD-L1 immunohistochemistry assays. For patients with mUC, formalin-fixed paraffin-embedded tumor samples were evaluated with Dako 22C3 and Ventana SP263 PD-L1 immunohistochemistry assays.
The majority (29/32; 91%) of mRCC cases were concordant between assays. The majority (17/18; 94%) of mUC cases were also concordant between assays.
There was strong concordance between PD-L1 assays chosen for comparison in both mRCC and mUC, with similar performance characteristics. One limitation is the small number of cases in this study; larger comparison studies are needed for this biomarker in mRCC and mUC.

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