PDCD1 and head and neck squamous cell carcinoma: Meta-analysis of 18 trials (9,748 patients) regarding an effect on PFS of anti-PD-1/PD-L1 mAbs (10 trials with nivolumab, 6 with pembrolizumab, and 2 with atezolizumab) in patients with gastric or gastro-esophageal junction cancer (2 studies), head-and-neck squamous cell carcinoma (1 study), melanoma (6 studies), NSCLC (7 studies), RCC (1 study), and urothelial cancer (1 study) showed improved PFS (HR = 0.73, 95% CI 0.65 to 0.84; p < 0.001).