CD274 and head and neck squamous cell carcinoma: In a retrospective study analyzing 12 clinical trials including over 1770 patients with solid tumors (including 235 HNSCC patients) treated with pembrolizumab, a high mutational burden (with a cut-off value of 175 mutations/exome) was associated with improved ORR (p = 0.016), PFS (p < 0.005), and OS (p = 0.029), independent of PD-L1 expression [57].