Faculty Bibliography

PURPOSE: To explore the role of whole-lesion apparent diffusion coefficient (ADC) analysis for predicting outcomes in prostate cancer patients on active surveillance. METHODS: This study included 72 prostate cancer patients who underwent MRI-ultrasound fusion-targeted biopsy at the initiation of active surveillance, had a visible MRI lesion in the region of tumor on biopsy, and underwent 3T baseline and follow-up MRI examinations separated by at least one year. Thirty of the patients also underwent an additional MRI-ultrasound fusion-targeted biopsy after the follow-up MRI. Whole-lesion ADC metrics and lesion volumes were computed from 3D whole-lesion volumes-of-interest placed on lesions on the baseline and follow-up ADC maps. The percent change in lesion volume on the ADC map between the serial examinations was computed. Statistical analysis included unpaired t tests, ROC analysis, and Fisher's exact test. RESULTS: Baseline mean ADC, ADC0-10th-percentile, ADC10-25th-percentile, and ADC25-50th-percentile were all significantly lower in lesions exhibiting >/=50% growth on the ADC map compared with remaining lesions (all P /=50% growth observed for ADC0-10th-percentile (585 +/- 308 vs. 911 +/- 336; P = 0.001). ADC0-10th-percentile achieved highest performance for predicting >/=50% growth (AUC = 0.754). Mean percent change in tumor volume on the ADC map was 62.3% +/- 26.9% in patients with GS >/= 3 + 4 on follow-up biopsy compared with 3.6% +/- 64.6% in remaining patients (P = 0.050). CONCLUSION: Our preliminary results suggest a role for 3D whole-lesion ADC analysis in prostate cancer active surveillance.

PURPOSE OF REVIEW: We review recent literature surrounding the use of prebiopsy prostate MRI and MRI-targeted biopsy in men at risk for prostate cancer. RECENT FINDINGS: Large series have strengthened the case for the use of MRI prior to prostate biopsy to maximize the detection of clinically significant disease, reduce the detection of clinically insignificant disease, and allow for tumor localization during targeted biopsy. Prebiopsy MRI followed by targeted biopsy appears to have the ability to overcome the limitations of the standard 12-core template. Use of MRI and targeted biopsy in the setting of a prior negative biopsy is supported by the literature and a recent consensus statement by the American Urological Association and the Society of Abdominal Radiology Prostate Cancer Disease-Focused Panel but is contingent upon the availability and quality of multiparametric MRI acquisition and interpretation. In men with no previous biopsy, MRI and targeted biopsy appears to increase detection of clinically significant disease compared with systematic biopsy while reducing detection of indolent disease. The addition of prostate cancer biomarkers and predictive nomograms may further enhance prebiopsy risk assessment. SUMMARY: Prostate MRI prior to biopsy may guide counseling regarding prostate cancer risk, allow for accurate tumor localization during targeted biopsy, and increase detection of clinically significant cancer while limiting detection of indolent disease. Its use prior to biopsy, in conjunction with biomarkers and predictive nomograms, may allow deferral of biopsy in select cases.

PURPOSE: To assess the impact of patient race and age on the performance of apparent diffusion coefficient (ADC) values for assessment of prostate cancer aggressiveness. MATERIALS AND METHODS: 457 prostate cancer patients who underwent 3T phased-array coil prostate MRI including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Mean ADC of a single dominant lesion was measured in each patient, using histopathologic findings from the prostatectomy specimen as reference. In subsets defined by race and age, ADC values were compared between Gleason score (GS) /= 4 + 3 tumors. RESULTS: 81% of patients were Caucasian, 12% African-American, 7% Asian-American. 13% were <55 years, 42% 55-64 years, 41% 65-74 years, and 4% >/=75 years. 63% were GS /= 4 + 3. ADC was significantly lower in GS >/= 4 + 3 tumors than in GS /= 4 + 3 as well as optimal ADC threshold was Caucasian: 0.73//=75 years, 0.79//=75 years than <55 years or 55-64 years (100.0% vs. 53.6%-73.3%; P < 0.001). CONCLUSION: Patients' race and age may impact the diagnostic performance and optimal threshold when applying ADC values for evaluation of prostate cancer aggressiveness.

OBJECTIVE: Prior studies in prostate diffusion-weighted magnetic resonance imaging (MRI) have largely explored the impact of b-value and diffusion directions on estimated diffusion coefficient D. Here we suggest varying diffusion time, t, to study time-dependent D(t) in prostate cancer, thereby adding an extra dimension in the development of prostate cancer biomarkers. METHODS: Thirty-eight patients with peripheral zone prostate cancer underwent 3-T MRI using an external-array coil and a diffusion-weighted image sequence acquired for b = 0, as well as along 12 noncollinear gradient directions for b = 500 s/mm using stimulated echo acquisition mode (STEAM) diffusion tensor imaging (DTI). For this sequence, 6 diffusion times ranging from 20.8 to 350 milliseconds were acquired. Tumors were classified as low-grade (Gleason score [GS] 3 + 3; n = 11), intermediate-grade (GS 3 + 4; n = 16), and high-grade (GS >/=4 + 3; n = 11). Benign peripheral zone and transition zone were also studied. RESULTS: Apparent diffusion coefficient (ADC) D(t) decreased with increasing t in all zones of the prostate, though the rate of decay in D(t) was different between sampled zones. Analysis of variance and area under the curve analyses suggested better differentiation of tumor grades at shorter t. Fractional anisotropy (FA) increased with t for all regions of interest. On average, highest FA was observed within GS 3 + 3 tumors. CONCLUSIONS: There is a measurable time dependence of ADC in prostate cancer, which is dependent on the underlying tissue and Gleason score. Therefore, there may be an optimal selection of t for prediction of tumor grade using ADC. Controlling t should allow ADC to achieve greater reproducibility between different sites and vendors. Intentionally varying t enables targeted exploration of D(t), a previously overlooked biophysical phenomenon in the prostate. Its further microstructural understanding and modeling may lead to novel diffusion-derived biomarkers.

Improvements in prostate MR imaging techniques and the introduction of MR imaging-targeted biopsies have had central roles in prostate cancer (PCa) management. The role of MR imaging has progressed from largely staging patients with biopsy-proven PCa to detecting, characterizing, and guiding the biopsy of suspected PCa. These diagnostic advances, combined with improved therapeutic interventions, have led to a more sophisticated and individually tailored approach to patients' unique PCa profile. This review discusses the MR imaging, a standardized reporting scheme, and the role of fusion-targeted prostate biopsy.

OBJECTIVE: The purpose of this study is to evaluate the roles of self-directed learning and continual feedback in the learning curve for tumor detection by novice readers of prostate MRI. MATERIALS AND METHODS: A total of 124 prostate MRI examinations classified as positive (n = 52; single Prostate Imaging Reporting and Data System [PI-RADS] category 3 or higher lesion showing Gleason score >/= 7 tumor at MRI-targeted biopsy) or negative (n = 72; PI-RADS category 2 or lower and negative biopsy) for detectable tumor were included. These were divided into four equal-sized batches, each with matching numbers of positive and negative examinations. Six second-year radiology residents reviewed examinations to localize tumors. Three of the six readers received feedback after each examination showing the preceding case's solution. The learning curve, plotting accuracy over time, was assessed by the Akaike information criterion (AIC). Logistic regression and mixed-model ANOVA were performed. RESULTS: For readers with and without feedback, the learning curve exhibited an initial rapid improvement that slowed after 40 examinations (change in AIC > 0.2%). Accuracy improved from 58.1% (batch 1) to 71.0-75.3% (batches 2-4) without feedback and from 58.1% to 72.0-77.4% with feedback (p = 0.027-0.046), without a difference in the extent of improvement (p = 0.800). Specificity improved from 53.7% to 68.5-81.5% without feedback and from 55.6% to 74.1-81.5% with feedback (p = 0.006-0.010), without a difference in the extent of improvement (p = 0.891). Sensitivity improved from 59.0-61.5% (batches 1-2) to 71.8-76.9% (batches 3-4) with feedback (p = 0.052), though did not improve without feedback (p = 0.602). Sensitivity for transition zone tumors exhibited larger changes (p = 0.024) with feedback than without feedback. Sensitivity for peripheral zone tumors did not improve in either group (p > 0.3). Reader confidence increased only with feedback (p < 0.001). CONCLUSION: The learning curve in prostate tumor detection largely reflected self-directed learning. Continual feedback had a lesser effect. Clinical prostate MRI interpretation by novice radiologists warrants caution.

OBJECTIVE: To determine how ipsilateral (ipsi) and contralateral (contra) systematic biopsies (SB) impacts detection of clinically significant versus insignificant prostate cancer (PCa) in men with unilateral MRI lesion undergoing MRI fusion target biopsy (MRF-TB). MATERIALS AND METHODS: 211 cases with one unilateral MRI lesion were subjected to SB and MRF-TB. Biopsy tissue cores from the MRF-TB, ipsi-SB and contra-SB were analyzed separately. RESULTS: A direct relationship was observed between MRI suspicious score (SS) and detection of any cancer, Gleason 6 PCa and Gleason > 6 PCa. MRF-TB alone, MRF-TB + ipsi-SB and MRF-TB + contra-SB detected 64.1%, 89.1% and 76.1% of all PCa, respectively, 53.5%, 81.4% and 69.8% of Gleason 6 PCa, respectively, and 73.5%, 96.0% and 81.6% of Gleason >6 PCa, respectively. MRF-TB + ipsi-SB detected 96% of clinically significant PCa and avoided detection of 18.6% of clinically insignificant PCa. MRF-TB + contra-SB detected 81.6% of clinically significant PCa and avoided detection of 30.2% of clinically insignificant PCa. CONCLUSION: Our study suggests that ipsi-SB should be added to MRF-TB as detection of clinically significant PCa increases with only a modest increase in clinically insignificant PCa detection. Contra-SB in this setting may be deferred since it primarily detects clinically insignificant PCa.

Purpose To test the impact of existing Prostate Imaging Reporting and Data System (PI-RADS) version 2 (V2) decision rules, as well as of proposed adjustments to these decision rules, on detection of Gleason score (GS) 7 or greater (GS >/=7) prostate cancer. Materials and Methods Two radiologists independently provided PI-RADS V2 scores for the dominant lesion on 343 prostate magnetic resonance (MR) examinations. Diagnostic performance for GS >/=7 tumor was assessed by using MR imaging-ultrasonography fusion-targeted biopsy as the reference. The impact of existing PI-RADS V2 decision rules, as well as a series of exploratory proposed adjustments, on the frequency of GS >/=7 tumor detection, was evaluated. Results A total of 210 lesions were benign, 43 were GS 6, and 90 were GS >/=7. Lesions were GS >/=7 in 0%-4.1% of PI-RADS categories 1 and 2, 11.4%-27.1% of PI-RADS category 3, 44.4%-49.3% of PI-RADS category 4, and 72.1%-73.7% of PI-RADS category 5 lesions. PI-RADS category 4 or greater had sensitivity of 78.9%-87.8% and specificity of 75.5%-79.1 for detecting GS >/=7 tumor. The frequency of GS >/=7 tumor for existing PI-RADS V2 decision rules was 30.0%-33.3% in peripheral zone (PZ) lesions upgraded from category 3 to 4 based on dynamic contrast enhancement (DCE) score of positive; 50.0%-66.7% in transition zone (TZ) lesions upgraded from category 3 to 4 based on diffusion-weighted imaging (DWI) score of 5; and 71.7%-72.7% of lesions in both zones upgraded from category 4 to 5 based on size of 15 mm or greater. The frequency of GS >/=7 tumor for proposed adjustments to the decision rules was 30.0%-60.0% for TZ lesions upgraded from category 3 to 4 based on DWI score of 4; 33.3%-57.1% for TZ lesions upgraded from category 3 to 4 based on DCE score of positive when incorporating new criteria (unencapsulated sheetlike enhancement) for DCE score of positive in TZ; and 56.4%-61.9% for lesions in both zones upgraded from category 4 to 5 based on size of 10-14 mm. Other proposed adjustments yielded GS >/=7 tumor in less than 15% of cases for one or more readers. Conclusion Existing PI-RADS V2 decision rules exhibited reasonable performance in detecting GS >/=7 tumor. Several proposed adjustments to the criteria (in TZ, upgrading category 3 to 4 based on DWI score of 4 or modified DCE score of positive; in PZ or TZ, upgrading category 4 to 5 based on size of 10-14 mm) may also have value for this purpose. (c) RSNA, 2016 Online supplemental material is available for this article.

PURPOSE: To assess the effects of temporal resolution (RT ) in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on qualitative tumor detection and quantitative pharmacokinetic parameters in prostate cancer. MATERIALS AND METHODS: This retrospective Institutional Review Board (IRB)-approved study included 58 men (64 +/- 7 years). They underwent 3T prostate MRI showing dominant peripheral zone (PZ) tumors (24 with Gleason >/= 4 + 3), prior to prostatectomy. Continuously acquired DCE utilizing GRASP (Golden-angle RAdial Sparse Parallel) was retrospectively reconstructed at RT of 1.4 sec, 3.7 sec, 6.0 sec, 9.7 sec, and 14.9 sec. A reader placed volumes-of-interest on dominant tumors and benign PZ, generating quantitative pharmacokinetic parameters (ktrans , ve ) at each RT . Two blinded readers assessed each RT for lesion presence, location, conspicuity, and reader confidence on a 5-point scale. Data were assessed by mixed-model analysis of variance (ANOVA), generalized estimating equation (GEE), and receiver operating characteristic (ROC) analysis. RESULTS: RT did not affect sensitivity (R1all : 69.0%-72.4%, all Padj = 1.000; R1GS>/=4 + 3 : 83.3-91.7%, all Padj = 1.000; R2all : 60.3-69.0%, all Padj = 1.000; R2GS>/=4 + 3 : 58.3%-79.2%, all Padj = 1.000). R1 reported greater conspicuity of GS >/= 4 + 3 tumors at RT of 1.4 sec vs. 14.9 sec (4.29 +/- 1.23 vs. 3.46 +/- 1.44; Padj = 0.029). No other tumor conspicuity pairwise comparison reached significance (R1all : 2.98-3.43, all Padj >/= 0.205; R2all : 2.57-3.19, all Padj >/= 0.059; R1GS>/=4 + 3 : 3.46-4.29, all other Padj >/= 0.156; R2GS>/=4 + 3 : 2.92-3.71, all Padj >/= 0.439). There was no effect of RT on reader confidence (R1all : 3.17-3.34, all Padj = 1.000; R2all : 2.83-3.19, all Padj >/= 0.801; R1GS>/=4 + 3 : 3.79-4.21, all Padj = 1.000; R2GS>/=4 + 3 : 3.13-3.79, all Padj = 1.000). ktrans and ve of tumor and benign tissue did not differ across RT (all adjusted P values [Padj ] = 1.000). RT did not significantly affect area under the curve (AUC) of Ktrans or ve for differentiating tumor from benign (all Padj = 1.000). CONCLUSION: Current PI-RADS recommendations for RT of 10 seconds may be sufficient, with further reduction to the stated PI-RADS preference of RT