Cancer progresses through the immune elimination, equilibrium, and escape phases. Tumors recruit regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), which suppress immune responses via cytokine secretion and the induction of the expression of PD-L1 in the tumor immune microenvironment. In an analysis of 91 patients with laryngeal squamous cell carcinoma treated with chemoradiotherapy (CRT), those with a high pre-treatment CD8/FOXP3 ratio demonstrated significantly better local control rates, particularly PD-L1-negative cases. The CD8/FOXP3 ratio is considered a useful indicator of the tumor immune status, and its evaluation in combination with the expression of PD-L1 is important. Among 30 patients who underwent CRT and developed local recurrence, a comparison of immune parameters before and after treatment revealed a positive correlation between changes in CD8+ tumor-infiltrating lymphocyte (TIL) density and the expression of PD-L1. Patients in whom both parameters were increased had higher survival rates.
These findings suggest that the pre-treatment CD8/FOXP3 ratio and expression of PD-L1 may be useful for predicting radiosensitivity and that positive changes in both CD8+ TIL density and the expression of PD-L1 after treatment may be predictive of improved survival outcomes. Further validation using large-scale studies is required.
