A phase II trial reported promising results for a second-line combination in cancer of unknown primary: an anti-PD-1 immune checkpoint inhibitor plus nab-paclitaxel. The study was led by Zhang and colleagues and described a regimen intended for CUP patients after prior therapy. For CUP—where tumor tissue origin is not identified—effective immunotherapy-based strategies have been a key focus. Adding chemotherapy to checkpoint inhibition can broaden immunogenicity and improve response likelihood, though the trial details and durability will drive clinical relevance. The results support further exploration of CUP regimens that can be applied despite heterogeneous underlying biology, potentially helping define evidence for treatment sequencing in this difficult-to-diagnose disease segment.