Presentation Authors: Eric Kim*, Dengfeng Cao, Joseph Ippolito, Russell Pachynski, Gerald Andriole, St. Louis, MO
Introduction: Recently, the clinical use of prostate multiparametric magnetic resonance imaging (mpMRI) has been increasingly adopted for the diagnosis of prostate cancer (PCa). However, false positives and false negatives occur not uncommonly. The potential cellular mechanisms responsible for this discrepancy have not been experimentally explored. We examined the influence of one potential cellular mechanismâ€”immune cell infiltrationâ€”on prostate mpMRI appearance.
Methods: With Institutional Review Board approval, we identified patients who had prostate mpMRI and subsequently underwent a MRI/US software fusion biopsy. Biopsies were performed with the UroNav platform (Invivo Corporation, Gainesville, FL). We included patients with PI-RADS classification 4 or 5 lesions. We excluded patients with a clinical history of prostatitis, prior biopsy within six months of mpMRI, multiple lesions, and small lesions ( < 0.25 mL) that may result in technical miss at the time of biopsy. We obtained two cores from each patient â€“ from the MRI targeted biopsy (MRI+) and from a systematic biopsy that was geometrically distant from the mpMRI lesion (MRI-). Biopsy specimens were stained for a pan-leukocyte marker (CD45) as well as a B cell marker (CD20). Leukocyte density (LD) was measured by a pathologist blinded to the mpMRI as number of cells per mm of biopsy core.
Results: We included 23 patients for this study. We found that the mean LD was significantly higher in MRI+ cores than for MRI- cores (71.9Â±25.4 versus 42.1Â±10.6 cells/mm, p=0.039). We also found that there was no difference between mean LD for MRI+ cores with PCa and MRI+ cores with no cancer (71.8Â±55.2 versus 72.0Â±77.5 cells/mm, p=0.99). These findings are summarized in Figure 1. Finally, for the subset of patients with MRI+ cores with PCa and MRI- cores without cancer (n=10), we found that CD20+ B cells were disproportionally represented in the MRI+ cores (13.7 versus 2.9% of the total leukocytes, p=0.138).
Conclusions: The immune cell composition within the prostate (whether it is benign or associated with PCa) contributes to prostate mpMRI appearance. In patients where prostate mpMRI detects PCa successfully, B cells are disproportionately represented, suggesting their role in the tumor microenvironment of PCa that can be seen on mpMRI.
Source of Funding: Funded in part through a grant from the Midwest Stone Institute