Presentation Authors: Daniel Artenstein, Aaron Krug*, Los Angeles, CA, Eugene Rhee, San Diego, CA, Ron Loo, Downey, CA, Stephen Williams, Polina Reyblat, Rex Parker, David Finley, Los Angeles, CA
Introduction: DNA promoter hypermethylation (Confirm MDX) may pick up occult prostate cancer due to a field defect the tumor exerts on normal tissue. The reported negative predictive value of Confirm MDX is high, ranging from 90-96% for low and high-grade cancer, respectively. In this study, we obtained MRI on all patients with a negative Confirm MDX to correlate imaging findings. We asked whether MRI can safely be omitted in the setting of a negative Confirm MDX.
Methods: All patients with elevated PSA and negative systematic prostate needle biopsy within 24 months of referral prospectively underwent Confirm MDX tissue testing (MDX) and 1.5 Tesla multiparametric MRI (no endorectal coil). MRI was centrally re-reviewed and PIRADS v.2 score was assigned to suspicious regions of interest (ROI). PIRADS 3 or higher lesions were considered abnormal. Clinicopathologic and imaging characteristics were analyzed.
Results: 113 patients underwent MDX and MRI. MDX was negative (MDX-) in 56 patients (49.6%). Among MDX-, MRI was negative (MRI-) in 40 (71.4%). Of the MRI+ patients, PIRADS 3-5 lesions were detected at a frequency of 56.25%, 31.25%, and 12.5%, respectively. Variables that correlated with a negative MRI included low PSA (7.82 ng/dL vs 11.2 ng/dL, p =0.033), lower PSA density ([PSAD] 0.13 ng/dL/mL vs. 0.21 ng/dL/mL, p=0.12), and smaller prostate volume (67.8 mL vs. 98.2 mL, p=0.028). Prostate volume among PIRADS 3, 4, and 5 lesions was 88.5 mL, 133.5 mL, and 30.6 mL, respectively. ROI diameter in each group measured 10.9 mm, 12.5 mm, and 24 mm. PIRADS 3, 4, and 5 lesions were identified in the transition zone in 75%, 0%, and 0% of cases. Of note, both PIRADS 5 lesions were located in the anterior base of the prostate; the MDX tissue samples in both patients only included the anterior apex.
Conclusions: The majority of Confirm MDX negative patients also had a negative mpMRI at 1.5T. Of patients with an abnormal MRI, most were PIRADS 3 transition zone lesions in large glands which historically rarely harbor prostate cancer. PSA < 10 and smaller gland size were significant predictors of negative MRI in the negative MDX patients. Anterior prostate cancers may be detected less often by Confirm MDX due to inadequate anterior prostate sampling at biopsy.