PD-L1 expression and surgical outcomes of adenosquamous carcinoma of the pancreas in a single-centre study of 56 lesions: PD-L1 expression in adenosquamous carcinoma of the pancreas

Objective: Adenosquamous carcinoma of the pancreas (ASCP) is a rare histologic subtype of pancreatic carcinoma. The clinicopathologic characteristics and surgical outcomes of ASCP are poorly understood due to the rarity of this disease. Recently, promising clinical responses in patients with pancreatic cancer have been obtained for antibodies against programmed death-1/programmed death-ligand 1 (PD-1/PD-L1). This study investigated the prevalence of PD-L1 expression and surgical outcomes of 56 ASCPs compared to 100 pancreatic ductal adenocarcinomas (PDACs). Methods: A total of 56 resected cases of ASCPs were retrospectively reviewed; after matching for the T category, 100 PDACs were selected as a control group for comparison. Immunohistochemistry for p53, Smad4, and PD-L1 was performed in both groups. Results: The ASCPs exhibited distinct clinicopathologic features, such as larger tumour, location in the distal pancreas, frequent vascular invasion and distant metastasis. In survival analysis, 1-and 2-year overall survival (OS) rates were 51.8% and 17.9%, respectively, with a median follow-up 13 months. According to multivariate analysis, vascular invasion and T category remained independent predictors of OS. Patients with ASCPs showed poorer survival than patients with PDACs after matching for the T category (p = 0.03). p53 and Smad4 were aberrantly expressed in 42 (75%) and 28 (50%) cases, respectively. Under the condition of a 10% cut-off value for PD-L1 positivity, approximately 11% of ASCPs were positive for PD-L1. Conclusions: Approximately 11% of patients with ASCPs are assumed to be potential candidates for the application of antibodies against PD-1/PD-L1, as based on the immunohistochemical results for PD-L1.