Single-cell analysis reveals clonally expanded tumor-associated CD57 + CD8 T cells are enriched in the periphery of patients with metastatic urothelial cancer responding to PD-L1 blockade.

CD8 T cells is reflective of an ongoing antitumor T-cell response. Our findings provide evidence and rationale for using circulating CD8 T cells expressing CD57 as a readily accessible blood-based biomarker for selecting patients with mUC for atezolizumab therapy.