Prognostic significance of programmed cell death 1 expression on CD8+T cells in various cancers: a systematic review and meta-analysis - Wan, Zhiyong; Cui, Meng; Yang, Jia; Liao, Dan; Chen, Junliang; Li, Fanmin; Xiang, Yin; Cui, Zhiwei; Yang, Yang (Frontiers in Oncology, 2025)