Researchers reported promising Phase II data for cancer of unknown primary (CUP) using a second-line regimen combining an anti–PD-1 immune checkpoint inhibitor with nab-paclitaxel. The study, led by Zhang, Zhao and Xu, evaluated the combination after prior therapy in CUP patients where tumor origin is not identified. The trial focused on the feasibility and early efficacy of the approach in CUP, a setting that often limits treatment selection and drives reliance on empiric or histology-guided options. Results were framed as clinically relevant for clinicians considering a pragmatic second-line option for CUP, where durable responses are difficult to achieve with standard strategies.