PDCD1 and head and neck squamous cell carcinoma: Finally, to validate the performance of the PFS-RF14 classifier in an independent cohort, we identified 30 additional patients with HNSCC (16 V-negative, 14 V-positive; see clinical data in Supplemental Table 2) treated at our center with anti–PD-1 drugs, who had complete clinical and genomic data available for analysis.