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

Programmed death ligand 1 (PD-L1) expression has predictive value for response to immune-checkpoint inhibitor treatment in urothelial cancer patients. The consistency of PD-L1 expression among different specimen types, however, is unknown. The aim of this 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 of 97 (15.5%) TURB, 17 of 98 (17.3%) cystectomies and nine of 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 neoadjuvant therapy (53.3% versus 25.4%; P = 0.03), and was not associated with other clinicopathological 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 neoadjuvant therapy. Therefore, immune-checkpoint inhibitor studies should take into account specimen type and neoadjuvant therapy in assessing the predictive value of PD-L1 expression.