The baseline circulating immunophenotype characteristics associate with PD(L)-1 targeted treatment response, irae onset, and prognosis.

More promising, effective, and less-invasive biomarkers for PD(L)-1 targeted responses, immune-related adverse events (irAEs), and prognosis are being explored. We conducted a single-center retrospective study in pan-cancer patients with anti-PD(L)-1 monotherapy. Observational endpoints included treatment response, prognosis, and irAEs. Peripheral blood immunophenotypes were analyzed by Flow Cytometry. 104 patients were enrolled. Higher pretreatment percentages of CD3(+)CD4(+) Th cells were associated with both responses (HR: 6.170, P = 0.034) and prognosis (HR: 1.930, P = 0.022). The higher baseline percentage of CD16(+)CD56(+) NK cells was positively correlated with response (HR: 3.730, P = 0.050) and negatively related to irAEs (HR: 0.460, P = 0.012). Decreased pretreatment CD3(+) T cell counts were related to more irAEs (HR: 0.970, P = 0.026), while the percentage of CD3(+) T cells was negatively associated with prognosis (HR: 1.930, P = 0.022). The higher baseline cell counts of CD3(+)CD8(+) CTL, CD19(+) B, and the percentage of CD19(+) B cells might be related to more irAEs (P < 0.05). Significant correlation between duration of treatment (DOT) and prognosis, irAE and outcome was also confirmed (P < 0.0001). Our findings confirmed multiple baseline circulating immunophenotype characteristics were related to PD(L)-1 targeted response, irAE onset, and prognosis.