In another study, Duchemann and colleagues reported that the ratio of CD8+PD-1+ to CD4+PD-1+ cells (termed PD-1-expressing ratio of lymphocytes in a systemic blood sample, or PERLS) prior to therapy associated with patient outcome in advanced NSCLC patients (n = 111) receiving anti-PD-(L)1 [74]. Here, CD4 is linked to non-small cell lung carcinoma.