Predictive and Prognostic Role of PD-L1 in Urothelial Carcinoma Patients with Anti-PD-1/PD-L1 Therapy: A Systematic Review and Meta-Analysis

Recently, checkpoint inhibition of the PD-1/PD-L1 axis has been shown to be therapeutically relevant in urothelial carcinoma (UC). To evaluate the predictive and prognostic value of PD-L1 on response and survival in UC patients after cystectomy, chemotherapy, or anti-PD-1/PD-L1 therapy, a systematic review of PubMed, Embase, Web of Science, and the Cochrane Library was performed. A total of 2154 patients from 14 published studies were included. In all UC patients after cystectomy, tumour cell (TC) PD-L1 expression was not associated with the OS or PFS. For the subset of patients with organ-confined disease, TC PD-L1 expression significantly predicted OS after cystectomy (P = 0.0004). There was no significant evidence of an association between TC PD-L1 status and ORR or OS for UC patients treated with platinum-based chemotherapy. For UC patients treated with anti-PD-1/PD-L1 therapy, TC PD-L1 expression ≥ 5% could predict the response (P = 0.005), but not for the 1% cut-off (P ≥ 0.05). As for PD-L1 expression in tumour-inflating immune cells (TIICs), both subsets with IC2/3 vs. IC0/1 and IC1/2/3 vs. IC0 were associated with ORR to anti-PD-1/PD-L1 therapy. In the TIIC subset, IC2/3 vs. IC0/1 of PD-L1 was associated with higher CR (P = 0.002), PR (P = 0.04), and PD (P = 0.007). Further, higher TIIC PD-L1 status benefited from longer PFS (P < 0.001), but was not associated with OS in UC patients with anti-PD-1/PD-L1 therapy. Our study suggested that TIIC PD-L1 expression with 5% cut-off was valuable as a predictive and prognostic biomarker for ORR and PFS in UC patients with anti-PD-1/PD-L1 therapy.