Elevated serum soluble PD-L1 is associated with adverse outcomes after autologous stem cell transplantation in transplant-eligible multiple myeloma patients.

Multiple myeloma (MM) is a plasma-cell malignancy in which immune-evasion mechanisms may contribute to disease progression. Soluble programmed death-ligand 1 (PD-L1) has been associated with adverse outcomes in MM, but its prognostic significance before and after autologous stem cell transplantation (ASCT) remains incompletely defined. To evaluate serum PD-L1 concentrations before and six months after ASCT and to assess their associations with clinical outcomes, including overall survival (OS), disease-free survival (DFS), relapse, and graft failure. This prospective observational study included 40 transplant-eligible patients with MM treated at the Ain Shams University Bone Marrow Center. Serum PD-L1 was measured by ELISA before ASCT and six months after transplantation. Clinical outcomes were assessed during follow-up through 180 days, and associations with survival and adverse outcomes were evaluated using correlation analysis, Kaplan-Meier survival analysis, and receiver operating characteristic (ROC) analysis. Pre- and post-transplant PD-L1 levels were negatively correlated with OS (pre: r = -0.44, p = 0.004; post: r = -0.48, p = 0.002). Patients with relapse had higher pre- and post-transplant PD-L1 levels than those without relapse (119.2 vs. 74.6 pg/mL, p = 0.01; and 184.4 vs. 63.4 pg/mL, p = 0.01, respectively). Post-transplant PD-L1 was higher in patients with graft failure than in those without graft failure (178.7 vs. 87.5 pg/mL, p = 0.008). Kaplan-Meier analysis showed poorer OS and DFS among patients with higher PD-L1 according to the study cutoffs. In conclusion, higher serum PD-L1 levels before and after ASCT were associated with adverse clinical outcomes in this cohort. Given the small sample size, limited follow-up, single-center design, and multiple unadjusted comparisons, these findings should be considered exploratory and require validation in larger studies.