Immunotherapy is one of the most impacting innovations in modern oncology. It has been introduced in the last decade in clinical practice for the treatment of several solid tumors, including non-small cell lung cancer (NSCLC), melanoma, colorectal, breast cancer and others [[1], [2], [3], [4], [5]]. Several tissue biomarkers have been identified to guide the selection of patients to treat with immunotherapy agents, manly CTL4, Programmed Death Ligand 1 (PD-L1) and Microsatellite Instability (MSI), and various technologies, antibodies and scores have been approved for the immunohistochemical evaluation of their expression in clinical practice. Regarding PD-L1, the antibodies most used are the SP142 and SP263 clones (Ventana) and the 22C3 clone (Dako) [6].

PD-L1 is the only biomarker used for the selection of the immunotherapy treatment in patients with urothelial carcinoma (UC)according to the National Comprehensive Cancer Network guidelines [7]; in particular, administration of Pembrolizumab is indicated in cases with Combined Positive Score (CPS) PD-L1 score >10, Atezolizumab for those with Immune Cell (IC) score >5, and Nivolumab for those with Tumor Proportion Score (TPS) score >1 %; nevertheless, these cut-offs were identified in studies employing different PD-L1 antibodies and platforms, and no precise data are currently available on the concordance and interchangeability of these platforms. The aim of this study was to investigate the concordance between three different antibodies (SP142, SP263 and 22C3) analysed with two different technologies in evaluating the immunohistochemical expression of PD-L1 in advanced urothelial cancer.