Mp30-16 local immune modulation by decreasing cd4+ / cd8+ t cells ratio after prostate cancer hemi-cryoablation

Abstract

INTRODUCTION AND OBJECTIVES: While thermal ablationmight activate tumor-specific T cells by raising the presentation of tumorantigens, there is no information about prostate hemi-cryoablation onlocal immunology. In a wider perspective, at least three possibilities: 1)no clinical significance, 2) boost or 3) harm. Tumors escape from im-mune system via decreasing MHC-I expression and consequentlydecreasing CD8+ and increasing CD4+ T cells activity.METHODS: Prostate biopsies (12 cores) were collected from10 unilateral prostate cancer patients (T1c, PSA density < 0.15 ng/dl,Gleason grade group 1, ¼2 cancer biopsy cores and < 50% cancercore involvement) at diagnosis and 12 months after hemi-cryoablation.Cancer positive and negative lobes at diagnosis and the same areas 12months after hemi-cryoablation (Diag+, Diag-, Cryo+, Cryo-, respec-tively) were explored by immunohistochemistry for infiltrating CD4+ Thelper and CD8+ T cytotoxic cells (in 45 random fields per prostate lobewith a 40x objective). The quantitative analysis of cells/mm2 and CD4+/CD8+ ratio were performed and compared among Diag+, Diag-, Cryo+,Cryo- using ImageJ software.RESULTS: There was a significant increase in tumor infiltratingCD8+ T cytotoxic cells/mm2 in the Cryo+ tissue (mean, SD: 0.31, 0.30)compared to Diag+ (0.18, 0.15), p¼0.015. In contrast, infiltrating CD4+T helper cells/mm2 presented a trend to decrease in Cryo+ (0.26, 0.27)compared to Diag+ (0.52, 0.38). Infiltrating CD4+ / CD8+ T cells ratioincreased after hemi-cryoablation.CONCLUSIONS: This is the first study to show local immunemodulation after prostate cancer cryoablation, characterized bydecreasing CD4+ / CD8+ T cells ratio with potential for clinical impact.Once previous studies have demonstrated correlation to cancer control,future studies are necessary to confirm current results, to exploredifferent energies and to correlate the local immunomodulation withoncological control.