Multicenter real-world data on immunotherapy for R/M HNSCC from China: comprehensive analysis of efficacy and survival differences across diverse clinical backgrounds, and identification of predictive peripheral blood biomarkers. - Sun F; Pu S; Hou B; Liu J; Liu C; Zang J; Su H; Wang Z; Song X; Wang S; Jiang D; Zhao L; et al. (Frontiers in immunology, 2026)