Low intratumoral regulatory T cells and high peritumoral CD8+ T cells relate to long-term survival in patients with pancreatic ductal adenocarcinoma after pancreatectomy

The prognosis for pancreatic ductal adenocarcinoma (PDAC) remains extremely poor. Recent studies have focused on the role of lymphocytes in the PDAC microenvironment. Using immunohistochemistry, our study explored the clinical significance of intratumoral or peritumoral CD4(+)Foxp3(+) regulatory T cells (Tregs) and CD8(+) T cells in the tumor microenvironment and analyzed their relation to the prognosis of PDAC in a consecutive series of 92 patients after resection. CD8(+) T cells were more frequently seen within peritumoral sites, while CD4(+)Foxp3(+) Tregs were more frequent within intratumoral areas. Neither exhibited any relationship with other clinicopathologic factors. Patients with low levels of intratumoral Tregs had longer disease-free survival than those with higher levels (DFS 22.2 vs. 11.2 months, p < 0.001), and patients with higher levels of peritumoral CD8(+) T cells had longer overall survival than those with lower levels (OS 31.0 vs. 14.2 months, p < 0.001). Multivariate analysis demonstrated that intratumoral Tregs (hazard ratio, HR 3.39, p = 0.010) and peritumoral CD8(+) T cells (HR 0.10, p < 0.001) are related to DFS and OS, respectively. These results indicate that intratumoral Tregs are a negative predictor of DFS, while peritumoral CD8(+) T cells are a positive predictor of OS for PDAC patients with pancreatectomy.