Prognostic Value of Immunohistochemical Expression of Programmed Death-Ligand 1 (PD-L1) in Pancreatic Ductal Adenocarcinoma.

Background: Pancreatic ductal adenocarcinoma is a highly aggressive
malignancy with an unfavorable prognosis. Immunotherapy targeting immune
checkpoints, particularly programmed death-ligand 1 (PD-L1), has
demonstrated promising results in various cancer cases. However, its prognostic
role in pancreatic ductal adenocarcinoma remains unclear. This study focused
on evaluating PD-L1 expression in tumor cells and tumor-infiltrating
lymphocytes using immunohistochemistry, and its association with
clinicopathological features and survival outcomes.
Materials and methods: This study was retrospectively conducted on 40
patients confirmed to have pancreatic ductal adenocarcinoma.
Immunohistochemistry was used to assess PD-L1 expression in both tumor cells
and associated immune cells within the tumor microenvironment. Tumor-
infiltrating lymphocytes were also evaluated. The correlations between PD-L1
expression and clinical, pathological, and survival outcomes were analyzed
using chi-square and Fisher’s exact tests. Overall survival and disease-free
survival were analyzed using the Kaplan–Meier method and compared with the
log-rank test.
Results: Expression of PD-L1 was observed in 27.5% of tumor cells and 40%
of tumor-infiltrating lymphocytes. A significant association was found between
PD-L1 expression in tumor cells and significantly correlated with poor
histological differentiation (p = 0.008) and the presence of lymph node
metastasis (p = 0.03). PD-L1 positivity in immune cells was significantly
correlated with higher tumor grade (p = 0.006), advanced stage (p = 0.04),
presence of lymphovascular invasion (p = 0.02), and lymph node involvement
(p = 0.02). A strong association was observed between expression of PD-L1 in
tumor cells and immune cells (p < 0.0001). Patients exhibiting PD-L1
expression in either compartment showed significantly reduced overall and
disease-free survival (p < 0.05). Elevated tumor-infiltrating lymphocytes levels
were also linked to adverse survival outcomes.
Conclusion: PD-L1 positivity in both tumor and immune cell populations is
linked to aggressive pathological features and poorer survival in pancreatic
ductal adenocarcinoma. These findings highlight PD-L1 as a potential
prognostic biomarker and support its role in identifying candidates for
immunotherapy. Further prospective studies are recommended to validate these
findings.