This meta-analysis found that using API treatment alone substantially improved OS in all cases of HNSCC (HR=0.85 (0.76, 0.95), I2= 26%, P=0.004) and also in cases having PD-L1 expression ≥1% (HR=O.74 (0.64, 0.86), I2= 0%, Z=3.90, P<0.0001); while compared to the participants treated with SOC. Here, CD274 is linked to head and neck squamous cell carcinoma.