Presentation Authors: Michael Witthaus, Matthew Truong*, Jacob Gantz, Thomas Frye, Ahmed Ghazi, Edward Messing, Jean Joseph, Hiroshi Miyamoto, Hani Rashid, Rochester, NY
Introduction: Negative prostate biopsies occur in up to 40% of cases following MR/US fusion targeted biopsy (TB) with concurrent systematic biopsy (SB) for PIRADS score â‰¥3 after at least one prior negative 12-core SB. Was the inability to detect prostate cancer (PCa) due to targeting error, inadequate sampling, or did the radiologist overcall the MRI lesion as positive? This perplexing situation leads to clinical uncertainty as to whether repeating another MR/US fusion biopsy session would be beneficial. In this study, we sought to determine whether ConfirmMDxÂ®, a validated DNA methylation field effect assay, would be clinically useful if applied to TB + SB cores with benign pathology.
Methods: In a retrospectively maintained database, we identified 142 consecutive patients who underwent MR/US fusion TB + SB for PIRADS â‰¥3 following at least one negative SB session. Multiparametric MRI was performed using a 3-Tesla scanner and scored using PI-RADS Version 2. Among the 142 patients who underwent biopsy, 65 patients had benign pathology and were offered subsequent ConfirmMDxÂ® testing of the benign TB + SB cores. ConfirmMDxÂ® was performed in a total 44 patients and alterations in GSTP1, APC, and RASSF1 correlated with abnormal regions of interest (ROI) on MRI based on corresponding sextant location.
Results: Among 44 patients who underwent ConfirmMDxÂ®, 18/44 (40.9%) exhibited DNA hypermethylation of either GSTP1, APC, or RASSF1, while 6/44 (13.6%) exhibited hypermethylation of least two genes. DNA hypermethylation of GSTP1, APC, or RASSF1 within and outside the ROI was observed in 7/44 (15.9%) and 14/44 (31.8%) of patients, respectively. There was no correlation between PIRADS score and hypermethylation status (p > 0.05).
Conclusions: Given that DNA hypermethylation of GSTP1, APC, and RASSF1 was uncommon in the benign tissue sampled from MRI-positive regions, repeating a TB will likely have low yield for detecting clinically significant PCa. In the future, sextant sampling of regions with field effects may be a more effective means of detecting occult PCa in this specific population of patients.