Diagnostic value of biparametric MRI as an adjunct to PSA-based detection of prostate cancer.

Abstract

193 Background: To determine the diagnostic yield of analyzing a fast, cost-conscious biparametric (T2 and diffusion-weighted) MRI (B-MRI) for prostate cancer (PCa) detection as an adjunct to to standard digital rectal exam (DRE) and prostate specific antigen (PSA)-based screening. Methods: Review of patients who were enrolled in a trial to undergo MP-MRI and MR/US fusion-guided prostate biopsy at our institution identified 143 men who underwent MP-MRI in addition to standard DRE and PSA-based PCa screening prior to any other prior prostate biopsy sessions. Patient demographics, DRE staging, PSA, PSA density (PSAD), and B-MRI findings were assessed for association with PCa detection on biopsy. Results: Men with detected PCa tended to be older, with higher PSA, higher PSAD, and increased number of screen positive lesions (#SPL) on B-MRI. B-MRI performed well for the detection of PCa with an area under the curve (AUC) of 0.80 (compared to 0.66 and 0.74 for PSA and PSAD). We derived PSA and MRI-based combined screening formulas for detection of PCa with optimized thresholds. (1) for PSA and B-MRI: PSA + 6 x (#SPL) > 14 and (2) for PSAD and B-MRI: 14 x (PSAD) + (#SPL) > 4.25. Area under the curve for equations 1 and 2 were 0.83 and 0.87 and overall accuracy of PCa detection was 79% in both models. Furthermore, the model integrating PSA with #SPL on B-MRI, was much more efficient at maximally identifying men with Gleason 7 or higher disease compared to PSA-screening alone. Use of model combining PSAD and MRI, the number of bGS 7 or higher cancers that were missed was minimized. Overall, combined use of PSA or PSAD coupled with B-MRI #SPL improved the true positive yield of identifying men with bGS 7 or higher while minimizing the false positive number of men identified as “screen-positive,” but with no cancer on biopsy. Conclusions: Number of positive lesions on B-MRI outperforms PSA alone in detecting PCa, supporting the use of this limited, non-contrast MRI as a potential adjunct tool in PCa screening. Furthermore, this imaging criteria coupled as an adjunct with PSA and PSAD, provides even more accuracy in detecting clinically-significant PCa.