In-Bore MRI-guided Prostate Biopsies in Patients with Prior Positive Transrectal US-guided Biopsy Results: Pathologic Outcomes and Predictors of Missed Cancers.

Purpose: To evaluate the role of confirmatory in-bore MRI-guided biopsy in patients with low- or intermediate-risk disease diagnosed at prior transrectal US-guided biopsy and to evaluate the rate and predictors for missed cancers. Materials and Methods: A retrospective evaluation of 50 consecutive men who had previously undergone transrectal US-guided biopsy with positive results and who underwent subsequent in-bore MRI-guided biopsy at our university hospital (average time interval, 11 months) between 2012 and 2016 was performed. Ten men were excluded because of a history of treatment after transrectal US-guided biopsy. A total of 40 men (mean age, 63 years; range, 47-84 years) were included in this study. Multiparametric 3-T MRI (T2-weighted, diffusion-weighted, and dynamic contrast material-enhanced) and transrectal in-bore MRI-guided biopsy were performed. Cancer detection, disease-grade changes, and cancers missed at in-bore MRI-guided biopsy were evaluated. Descriptive statistics were used to report different rates. The Fisher exact test was used for categoric variables. The Mann-Whitney U test and independent Student t test were used for nonparametric and parametric data, respectively. The McNemar test was used for paired data. Results: The overall cancer detection rate when using in-bore MRI-guided biopsy was 65% (26 of 40). In-bore MRI-guided biopsy detected 14 previously undiscovered cancerous lesions (clinically significant cancers [CSCs], 57.1% [eight of 14]). An overall disease upgrade by in-bore MRI-guided biopsy occurred in 40% (16 of 40) of cases (61.5% [16 of 26] of cases with positive results from in-bore MRI-guided biopsy). One case was downgraded from a Gleason score (GS) of 3 + 4 = 7 to a GS of 3 + 3 = 6. Out of 71 sextant biopsies with positive results detected by transrectal US-guided biopsy (from all 40 patients), 80% (57 of 71) were visible on MR images (in-bore MRI-guided biopsy results were positive in 52.6% [30 of 57]), and 20% (14 of 71) had no image correlates on MR images. In-bore MRI-guided biopsy upgraded 60% (18 of 30) and downgraded 3.3% (one of 30) of detected lesions. The false-negative rate was 35% (14.2% [two of 14] of patients had CSCs; GS ≥ 7), was higher in prostate volumes of greater than 40 mL, and was lower in the anterior gland location (P = .04 and .01, respectively). Conclusion: Performing confirmatory in-bore MRI-guided biopsy following positive transrectal US-guided biopsy resulted in a high disease-upgrade incidence with subsequently improved disease-risk stratification, particularly when considering patients for active surveillance or focal therapy. Supplemental material is available for this article. © RSNA, 2020See also the commentary by Weiss and Solomon in this issue.