PDCD1 and cancer: For example, the baseline CD4+/CD8+ T-cell ratio and its changes have been identified as prognostic markers for cancer patients (33, 55), although the findings of a recent study have provided evidence to indicate that the CD8+PD-1+ to CD4+PD-1+ T-cell ratio, rather than the CD8+/CD4+ T-cell ratio, is associated with clinical benefits in advanced NSCLC patients treated with ICIs (56).