Prognostic value of serum soluble programmed death-ligand 1 (sPDL1) and dynamics during chemotherapy in advanced gastric cancer patients.

4034 Background: The soluble form Programmed Death-Ligand 1(sPDL1) is suggested to have immunosuppressive activity and under investigation as candidate biomarker for immuno-oncology drug development. In this study, we measured the serum sPDL1 at pre-and post-chemotherapy and evaluated its prognostic implication and dynamics during chemotherapy in advanced gastric cancer (GC). Methods: We prospectively enrolled 68 GC patients who were candidates for palliative standard 1st-line chemotherapy, and blood was serially collected at pre-and post-one cycle of chemotherapy, at best response and disease progression. sPDL1 was measured using an enzyme-linked immunosorbent assay. Response to chemotherapy, overall survival (OS), progression-free survival (PFS) and other prognostic factors including neutrophil-lymphocyte ratio (NLR) were obtained. The cut-off values of sPDL1 levels and changes for survivals were found using C-statistics. Results: The median baseline sPDL1 was 0.8ng/mL(range, 0.06 - 6.06ng/mL). The median OS and PFS were 14.9 months (95% CI: 7.33-22.47) and 8.0 months (95% CI: 5.96-10.0), respectively. sPDL1 and NLR showed a positive correlation. Patients with low levels of sPD-L1 at diagnosis ( < 1.92 ng/mL) showed a better OS and PFS than the patients with a high sPDL1 (OS: 18.3 vs. 95 months, P = 0.057, PFS: 8.9 vs. 6.0 months, P = 0.04). The baseline sPDL1 before treatment were higher in the PD group than in the SD and PR groups (mean:2.91, 1.17, 1.19, P = 0.019). Patients whose sPDL1 increased after 1st cycle of chemotherapy showed the tendency of worse PFS and OS. When disease progressed, sPDL1 increased compared with baseline (mean:1.31, 1.45, P = 0.029). Conclusions: sPDL1 at pre-chemotherapy confers the prognostic value for PFS and OS in GC patients under palliative 1st-line chemotherapy. The dynamics of sPDL1 during chemotherapy correlates with disease courses.