PDCD1 and metastatic malignant neoplasm in the lymph nodes: When studies were stratified based on different PD-L1 expression levels, PD-L1 or PD-1 inhibitors, studied drugs, visceral or lymph node-only metastasis and in the upper or lower tract 9 [12–16, 19–22] studies reported the efficacy of PD-L1 inhibitors, with the pooled ORR being 0.18 (95% CI 0.15–0.21, I2 = 63.3%, P = 0.005).