Reduction of gender-associated M2-like tumor-associated macrophages in the tumor microenvironment of patients with pancreatic cancer after neoadjuvant chemoradiotherapy.

Purpose: This study aimed to investigate gender-dependent antitumor immune response to neoadjuvant chemoradiotherapy (NACRT) in pancreatic ductal adenocarcinoma (PDAC) patients.

Methods: This study enrolled 58 patients (25 females and 33 males) with borderline resectable PDAC who underwent R0 surgical resection after NACRT. The resected tumor specimens were analyzed for tumor-associated macrophages (TAMs); tumor-infiltrating lymphocytes (CD8+ and CD4+ T cells); regulatory T cells; and IRF-5-expressing cells using immunohistochemical staining for CD163, CD204, CD8, CD4, Foxp3, and IRF-5 antigen. The relationship between clinicopathological features and clinical outcomes was evaluated using multivariate Cox proportional hazard analysis.

Results: Females had longer overall survival (P = .044) and relapse-free survival (P = .044) than males. The CD204+ TAM number was significantly lower in females than in males (P = .009). No significant difference occurred between female and male patients in other tumor-infiltrating immune cells. IRF-5+ cell number was significantly higher in female patients (P = .002). Negative correlation occurred between CD204+ cells and IRF-5-positive cells (P = .003, r = -.385).

Conclusions: Female gender was an independent prognostic factor possibly due to the greater reduction in CD204+ TAM infiltration in tumors after NACRT. The beneficial effects of NACRT on TAMs' infiltration might be associated with gender-dependent IRF-5 expression.