Dynamics in the Prostate Immune Microenvironment Induced by Androgen Deprivation Therapy

Background: The influence of testosterone on the prostate's immune microenvironment remains unclear. This study aims to elucidate the dynamics of immune cells in the prostate following androgen deprivation therapy (ADT). Methods: We retrospectively compared prostate needle biopsy and radical prostatectomy specimens from 33 patients who underwent both procedures, along with neoadjuvant ADT at a single institution. Immune cell infiltration in the cancer and stroma areas was assessed using multiplex fluorescence immunohistochemistry. Results: Post-ADT, all immune cells, including CD4⁺ T cells, CD8⁺ T cells, Foxp3⁺ regulatory T cells, CD204⁺ macrophages, and CD20⁺ B cells, significantly increased in the prostatectomy specimen. However, few immune cells were detected in the biopsy of the same patients (p < 0.001). The number of CD20⁺ B cells in the cancer area was significantly lower post-ADT in high-risk cases according to the NCCN classification (p = 0.020). This difference was significantly associated with the Gleason Grade Group, rather than PSA levels or T classification (p < 0.001). However, no significant difference was observed in the recurrence rate between Grade Groups 1, 2, 3 and 4, 5 (p = 0.991). There was no significant difference in immune cells other than CD20⁺ B cells when divided into NCCN classifications. Conclusions: The marked increase in immune cells following ADT suggests an intensified immune response against prostate cancer.