Login to Access Video or Poster Abstract: MP70-19
Sources of Funding: None

Introduction

While thermal ablation might activate tumor-specific T cells by raising the presentation of tumor antigens to the immune system, there is no information about prostate hemi-cryoablation impact on local immunology.

Methods

Prostate biopsies were collected from 10 very low risk prostate cancer patients (T1c, PSA density <0.15 ng / dL, Gleason ≤6, ≤2 cancer biopsy cores and ≤50% involvement any core with cancer) at diagnosis and 12 months after hemi-cryoablation. Cancer positive and negative lobes at diagnosis and the same areas 12 months after hemi-cryoablation (Diag+, Diag-, Cryo+ and Cryo-, respectively) were explored using immunohistochemistry for tumor infiltrating CD4+ T helper and CD8+ T cytotoxic cells (counted in 45 fields per patient with a 40x objective). The quantitative analysis of cells/mm² and CD8+/CD4+ ratio were performed using ImageJ software.

Results

There was a significant increase in tumor infiltrating CD8+ T cytotoxic cells/mm² in post Cryo+ prostatic tissue (mean ± SD: 0.31 ± 0.30) compared to Diag+ (0.18 ± 0.15), p=0.015. In contrast, tumor infiltrating CD4+ T helper cells/mm² showed a tendency to decrease in Cryo+ (0.26 ± 0.27) compared to Diag + (0.38 ± 0.52). Tumor infiltrating T cytotoxic / T helper cells ratio increased after hemi-cryoablation, with conceivable anti-tumor immunity and favorable prognosis._x000D_ _x000D_

Conclusions

This is the first study to show positive local immune modulation after prostate cancer cryoablation, characterized by increasing T cytotoxic / T helper cells ratio with potential to boost antitumor immune response. Long term follow-up and wider cohorts might confirm potential clinical impact and if such modulation occurs for any ablation or for cryoablation only._x000D_ _x000D_

Funding

None