CD274 and digestive system cancer: A meta-analysis study involving 7308 digestive system cancer patients found that high expression of PD-L1 was associated with poor prognosis (HR = 1.44, 95% CI 1.18–1.76, P < 0.001), especially in GC (HR = 1.43, 95% CI 1.05–1.94, P = 0.021) [20].