Programmed Death-Ligand 1 Expression in a Large Cohort of Pediatric Patients With Solid Tumor and Association With Clinicopathologic Features in Neuroblastoma.

PURPOSE: Programmed death-ligand 1 (PD-L1) expression represents a potential predictive biomarker of immune checkpoint blockade response. However, literature about the prevalence of PD-L1 expression in the pediatric cancer setting is discordant. METHODS: PD-L1 expression was analyzed using immunohistochemistry in 500 pediatric tumors (including neuroblastoma, sarcomas, and brain cancers). Tumors with ≥ 1% cells showing PD-L1 membrane staining of any intensity were scored as positive. Positive cases were further characterized, with cases with weak intensity PD-L1 staining reported as having low PD-L1 expression and cases with a moderate or strong intensity of staining considered to have high PD-L1 expression. RESULTS: PD-L1-positive staining was identified in 13% of cases, whereas high PD-L1 expression was found in 3% of cases. Neuroblastoma (n = 254) showed PD-L1 expression of any intensity in 18.9% of cases and was associated with longer overall survival (P = .045). However, high PD-L1 expression in neuroblastoma (3.1%) was significantly associated with an increased risk of relapse (P = .002). Positive PD-L1 staining was observed more frequently in low- and intermediate-risk patients (P = .037) and in cases lacking MYCN amplification (P = .002). CONCLUSION: In summary, high PD-L1 expression in patients with neuroblastoma may represent an unfavorable prognostic factor associated with a higher risk of cancer relapse. This work proposes PD-L1 immunohistochemical assessment as a novel parameter for identifying patients with an increased likelihood of cancer recurrence.