CTLA4 and head and neck squamous cell carcinoma: There were no significant differences found with regard to the progression-free survival between age groups below or above 65 (HR = 1.13; 95% CI, 0.78 - 1.63; p = 0.49) (Figure 3A), between PD-1 and PD-L1 + CTLA-4 inhibitors (HR = 1.47; 95% CI, 0.82 - 2.63; p = 0.20) (Figure 3C), between PD-1 and PD-L1 inhibitors (HR = 1.09; 95% CI, 0.65 – 1.82; p = 0.75) (Figure 3C), between first line of treatment versus second line or more (HR = 0.90; 95% CI, 0.61 - 1.32; p = 0.59) (Figure 3D), or between metastatic or locoregionallly recurrent HNSCC (HR = 0.83; 95% CI, 0.58 - 1.20; p = 0.34) (Figure 3E).