Efficacy and safety of PD-1 inhibitors as second-line treatment for advanced squamous esophageal cancer: a systematic review and network meta-analysis with a focus on PD-L1 expression levels - Yang, Fei; Dan, Min; Shi, Jindan; Fan, Ling; Zhang, Haoluo; Jian, Tiantian; Lei, Kelu; Wang, Yue; Xin, Juan; Yu, Zhigang; Chen, Wei (Frontiers in Immunology, 2025)