Concordance of PD-L1 expression in matched urothelial bladder cancer specimens

Programmed Death-Ligand (PD-L1) expression has predictive value for response to immune-checkpoint inhibitor treatment in urothelial cancer patients. The consistency of PD-L1 expression amongst different specimen types is however unknown. The aim of the study is to compare PD-L1 expression in matched transurethral resections of the bladder (TURB), cystectomy specimens, and lymph node metastases of urothelial cancer patients.

We performed PD-L1 (SP142) immunohistochemistry on whole tissue slides of 115 urothelial carcinoma patients who had undergone TURB, followed by radical cystectomy and/or pelvic lymph node dissection. The PD-L1 assay was positive if PD-L1 expression in immune cells occupied ≥5% of the tumour area. PD-L1 was positive in 15/97 (15.5%) TURB, 17/98 (17.3%) cystectomies, and 9/49 (18.4%) lymph node metastases. Agreement of PD-L1 assay outcome between cystectomy and TURB (kappa 0.34; P=0.002), and cystectomy and lymph node metastasis (kappa 0.35; P=0.034) was fair; there was no agreement between TURB and lymph node metastasis (kappa 0.045; P=0.82). Discordance of PD-L1 outcome in matched TURB and cystectomy specimens occurred more frequently after neo-adjuvant therapy (53.3% versus 25.4%; P=0.03), and was not associated with other clinicopathologic parameters.

Urothelial bladder cancer patients showed fair agreement of PD-L1 assay outcome in cystectomies and matched TURB or lymph node specimens. PD-L1 expression was discordant more often after neo-adjuvant therapy. Therefore, immune-checkpoint inhibitor studies should take into account specimen type and neo-adjuvant therapy in assessing the predictive value of PD-L1 expression. This article is protected by copyright. All rights reserved.

Histopathology. 2018 Jul 12 [Epub ahead of print]

Joep J de Jong, Hans Stoop, Daan Nieboer, Joost L Boormans, Geert J L H van Leenders

Department of Pathology, Erasmus Medical Centre, Rotterdam, The Netherlands., Department of Public Health, Erasmus Medical Centre, Rotterdam, The Netherlands., Department of Urology, Erasmus Medical Centre, Rotterdam, The Netherlands.