Specifically, higher levels of LOX-1+PMN-MDSCs were significantly associated with worse PFS (HR = 3.422, 95% CI (1.312–2.148), p = 0.009) and OS (HR = 2.901, 95% CI (1.187–1.943), p = 0.018), underscoring the pivotal role of this immunosuppressive myeloid population in influencing the clinical outcome of (R/M) HNSCC patients undergoing anti–PD-1 immunotherapy. Here, PDCD1 is linked to head and neck squamous cell carcinoma.