PD-L1 Assay Concordance in Metastatic Renal Cell Carcinoma and Metastatic Urothelial Carcinoma

PD-L1 testing has been investigated as a biomarker in both kidney and bladder cancer for response to immune checkpoint inhibitors, but there are a number of commercially available immunohistochemistry PD-L1 expression assays with different antibodies and criteria for positivity. Our study sought to evaluate the concordance of multiple commercially available PD-L1 assays in cohorts of patients with metastatic renal cell carcinoma (mRCC, n=32) and metastatic urothelial carcinoma (mUC, n=18) treated at the Duke Cancer Institute with immune checkpoint blockade.

The mRCC and mUC tissue evaluated were from a primary tumor in 71.9% and 61.1% and mRCC was primarily clear cell histology (87.5%). Overall, we found 91% (29/32) concordance between Dako 28-8 and Ventana SP142 assays in mRCC and 94% (17/18) concordance between Dako 22C3 and Ventana SP263 assays in mUC. Interpretation of our study is limited because of the small sample size, but these results suggest that performance characteristics may be similar across different PD-L1 assays. This warrants further study and is clinically relevant given the proliferation of disparate companion diagnostic PD-L1 assays being evaluated in clinical trials.

Written by: Landon C. Brown, MD, Department of Medicine, School of Medicine, Duke University, Durham, NC; Duke Cancer Institute Center for Prostate and Urologic Cancers, Durham, NC, USA

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