Analysis of the relationship between immunological microenvironment and prognosis in pancreatic cancer

Immune cell infiltration in tumors can serve as a prognostic marker in many cancers; however, its role in pancreatic ductal adenocarcinoma (PDAC) remains understudied. In this retrospective study, we aimed to evaluate the prognostic significance of the immunological microenvironment and immune cell infiltration in PDAC, considering both preoperative clinicophysiological and postoperative clinicopathological factors. Furthermore, we evaluated the same analyses after excluding patients who had received neoadjuvant treatment for the subgroup analysis. We included 189 patients who underwent radical resection for pancreatic cancer between October 2007 and October 2015 at our center and an affiliated university hospital. Immunohistochemical staining for clusters of differentiation (CD3, CD8, CD19, and CD20) was performed on the largest cross-sectional area of the tumor specimens to quantify immune cell infiltration. Disease-free survival (DFS) and overall survival (OS) were analyzed for each antigen. Preoperative clinicophysiological and postoperative clinicopathological factors were compared based on positively labeled cell counts. Among the 189 patients, 114 were men (average age, 69.3 years). CD20- and CD8-positive cell counts were significantly associated with DFS (P=0.027) and OS (P=0.033), respectively. No significant differences were observed between groups in terms of T factor for CD8, tumor location, biliary decompression, albumin level, C-reactive protein level, hemoglobin level, N factor, or disease stage for CD20. Multivariate analyses identified disease stage (P=0.04) and CD20 expression (P=0.043) as independent predictors of DFS, while CD8 expression (P=0.016) was the only independent predictor of OS. These results indicate that high CD20 expression, reflecting B-cell infiltration, predicts DFS, whereas high CD8 expression, reflecting T-cell infiltration, predicts OS. Collectively, our findings suggest that the immunological microenvironment represents a potential prognostic factor in patients with PDAC.