Prostate cancer: can multiparametric MR imaging help identify patients who are candidates for active surveillance?

Detection of prostate cancer using temporal sequences of ultrasound data: a large clinical feasibility study

PURPOSE

This paper presents the results of a large study involving fusion prostate biopsies to demonstrate that temporal ultrasound can be used to accurately classify tissue labels identified in multi-parametric magnetic resonance imaging (mp-MRI) as suspicious for cancer.

METHODS

We use deep learning to analyze temporal ultrasound data obtained from 255 cancer foci identified in mp-MRI. Each target is sampled in axial and sagittal planes. A deep belief network is trained to automatically learn the high-level latent features of temporal ultrasound data. A support vector machine classifier is then applied to differentiate cancerous versus benign tissue, verified by histopathology. Data from 32 targets are used for the training, while the remaining 223 targets are used for testing.

RESULTS

Our results indicate that the distance between the biopsy target and the prostate boundary, and the agreement between axial and sagittal histopathology of each target impact the classification accuracy. In 84 test cores that are 5 mm or farther to the prostate boundary, and have consistent pathology outcomes in axial and sagittal biopsy planes, we achieve an area under the curve of 0.80. In contrast, all of these targets were labeled as moderately suspicious in mp-MR.

CONCLUSION

Using temporal ultrasound data in a fusion prostate biopsy study, we achieved a high classification accuracy specifically for moderately scored mp-MRI targets. These targets are clinically common and contribute to the high false-positive rates associated with mp-MRI for prostate cancer detection. Temporal ultrasound data combined with mp-MRI have the potential to reduce the number of unnecessary biopsies in fusion biopsy settings.

The role of MRI in active surveillance for prostate cancer

Approximately one in seven American men will be diagnosed with prostate cancer during his lifetime, and at least 50% of newly diagnosed patients will present with low-risk disease. In the last decade, the decision-making paradigm for management has shifted due to high rates of disease detection and overtreatment, attributed to prostate-specific antigen screening, with more men deferring definitive treatment for active surveillance. The advent of multiparametric magnetic resonance imaging (MP-MRI) and MRI/ transrectal ultrasound-guided fusion-guided prostate biopsy has refined the process of diagnosis, identifying patients with clinically-significant cancer and larger disease burden who would most likely benefit from intervention. In parallel, the utilization of MP-MRI in the surveillance of low-grade, low-volume disease is on the rise, reflecting support in a growing body of literature. The aim of this review is to appraise and summarize the data evaluating the role of magnetic resonance imaging in active surveillance for prostate cancer.

Prostate cancer risk stratification with magnetic resonance imaging

In recent years, multiparametric magnetic resonance imaging (mpMRI) has shown promise for prostate cancer (PCa) risk stratification. mpMRI, often followed by targeted biopsy, can be used to confirm low-grade disease before enrollment in active surveillance. In patients with intermediate or high-risk PCa, mpMRI can be used to inform surgical management. mpMRI has sensitivity of 44% to 87% for detection of clinically significant PCa and negative predictive value of 63% to 98% for exclusion of significant disease. In addition to tumor identification, mpMRI has also been shown to contribute significant incremental value to currently used clinical nomograms for predicting extraprostatic extension. In combination with conventional clinical criteria, accuracy of mpMRI for prediction of extraprostatic extension ranges from 92% to 94%, significantly higher than that achieved with clinical criteria alone. Supplemental sequences, such as diffusion-weighted imaging and dynamic contrast-enhanced imaging, allow quantitative evaluation of cancer-suspicious regions. Apparent diffusion coefficient appears to be an independent predictor of PCa aggressiveness. Addition of apparent diffusion coefficient to Epstein criteria may improve sensitivity for detection of significant PCa by as much as 16%. Limitations of mpMRI include variability in reporting, underestimation of PCa volume and failure to detect clinically significant disease in a small but significant number of cases.

Use of mpMRI in active surveillance for localized prostate cancer

INTRODUCTION

In an effort to limit prostate cancer (PCa) overdiagnosis and overtreatment, which have occurred in response to widespread prostate specific antigen testing, numerous strategies aimed at improved risk stratification of patients with PCa have evolved. Multiparametric magnetic resonance imaging (MRI) is being used in concert with prostate specific antigen testing and prostate biopsies to improve sensitivity and specificity of these tests. There are limited data on how multiparametric MRI can be incorporated into active surveillance (AS) protocols.

EVIDENCE ACQUISITION

A PubMed literature search of available English language publications on PCa, AS, and MRI was conducted. Appropriate articles were selected and included for review. Bibliographies were also used to expand our search.

EVIDENCE SYNTHESIS

Data from 41 studies were reviewed. AS inclusion criteria and protocols varied among studies, as did indications for use of MRI. Technological improvements are briefly highlighted. Studies are broadly categorized and discussed according to the role of MRI in patient selection, disease staging, and monitoring in AS protocols.

CONCLUSIONS

Although improvements in MRI technology have been useful for biopsy guidance and in the diagnosis and staging of PCa, this literature search demonstrates that more prospective research is needed, specifically regarding how this promising technology can be incorporated into AS protocols.

Multiparametric MRI of the prostate: diagnostic performance and interreader agreement of two scoring systems

OBJECTIVE

To compare the diagnostic accuracies and interreader agreements of the Prostate Imaging Reporting and Data System (PI-RADS) v. 2 and University of California San Francisco (UCSF) multiparametric prostate MRI scale for diagnosing clinically significant prostate cancer.

METHODS

This institutional review board-approved retrospective study included 49 males who had 1.5 T endorectal MRI and prostatectomy. Two radiologists scored suspicious lesions on MRI using PI-RADS v. 2 and the UCSF scale. Percent agreement, 2 × 2 tables and the area under the receiver operating characteristic curves (Az) were used to assess and compare the individual and overall scores of these scales. Interreader agreements were estimated with kappa statistics.

RESULTS

Reader 1 (R1) detected 78 lesions, and Reader 2 (R2) detected 80 lesions. Both identified 52 of 65 significant cancers. The Az for PI-RADS v. 2 and UCSF scale for R1 were 0.68 and 0.69 [T2 weighted imaging (T2WI)], 0.75 and 0.68 [diffusion-weighted imaging (DWI)] and 0.64 and 0.72 (overall score), respectively, and were 0.72 and 0.75 (T2WI), 0.73 and 0.67 (DWI) and 0.66 and 0.75 (overall score) for R2. The dynamic contrast-enhanced percent agreements between scales were 100% (R1) and 95% (R2). PI-RADS v. 2 DWI of R1 performed better than UCSF DWI (Az = 0.75 vs Az = 0.68; p = 0.05); no other differences were found. The interreader agreements were higher for PI-RADS v. 2 (T2WI: 0.56 vs 0.42; DWI: 0.60 vs 0.46; overall: 0.61 vs 0.42). The UCSF approach to derive the overall PI-RADS v. 2 scores increased the Az for the identification of significant cancer (R1 to 0.76, p < 0.05; R2 to 0.71, p = 0.35).

CONCLUSION

Although PI-RADS v. 2 DWI score may have a higher discriminatory performance than the UCSF scale counterpart to diagnose clinically significant cancer, the utilization of the UCSF scale weighing system for the integration of PI-RADS v. 2 individual parameter scores improved the accuracy its overall score.

ADVANCES IN KNOWLEDGE

PI-RADS v. 2 is moderately accurate for the identification of clinically significant prostate cancer, but the utilization of alternative approaches to derive the overall PI-RADS v. 2 score, including the one used by the UCSF system, may improve its diagnostic accuracy.

The significance of anterior prostate lesions on multiparametric magnetic resonance imaging in African-American men

INTRODUCTION

African-American (AA) men tend to harbor high-risk prostate cancer (PCa) and exhibit worse outcomes when compared to other groups. It has been postulated that AA men may harbor more anterior prostate lesions (APLs) that are undersampled by the standard transrectal ultrasound guided-biopsy (SBx), potentially resulting in greater degree of Gleason score (GS) upgrading at radical prostatectomy. We aimed to evaluate the detection rate of anterior PCa significance of APLs in AA men on multiparametric magnetic resonance imaging (mpMRI) and compare it to a matched cohort of White/Other (W/O) men.

MATERIALS AND METHODS

A review of 1,267 men who had an mpMRI with suspicious prostate lesions and who underwent magnetic resonance transrectal ultrasound fusion-guided biopsy (FBx) with concurrent SBx in the same biopsy session was performed. All AA men were matched to a control group of W/O using a 1:1 propensity score-matching algorithm with age, prostate-specific antigen, and prostate volume as matching variables. Logistic regression analysis was used to determine predictors of APLs in AA men.

RESULTS

Of the 195 AA men who underwent mpMRI, 93 (47.7%) men had a total of 109 APLs. Prior negative SBx was associated with the presence of APLs in AA men (Odds ratio = 1.81; 95% CI: 1.03-3.20; P = 0.04). On multivariate logistic regression analysis, smaller prostate (P = 0.001) and rising prostate-specific antigen (P = 0.007) were independent predictors of cancer-positive APLs in AA men. Comparative analysis of AA (93/195, 47.7%) vs. W/O (100/194, 52%) showed no difference in the rates of APLs (P = 0.44) or in cancer detection rate within those lesions or the distribution of GS within those cancers (P = 0.63) despite an overall higher cancer detection rate in AA men (AA: 124/195 [63.6%] vs. W/O: 97/194 [50.0%], P = 0.007). In cases where APLs were positive for PCa on FBx, the GS of APL was equal to the highest GS of the entire gland in 82.9% (29/35) and 90.9% (30/33) of the time in AA and W/O men, respectively.

CONCLUSION

Cancer-positive APLs represented the highest risk GS in most cases. AA men with prior negative SBx are twice as likely to harbor a concerning APL. In our cohort, AA and W/O men had comparable rates of APLs on mpMRI. Thus, differences in APLs do not explain the higher risk of AA men for deahth due to PCa. However, targeting of APLs via FBx can clinically improve PCa risk stratification and guide appropriate treatment options.

Risk stratification of prostate cancer in the modern era

PURPOSE OF REVIEW

Novel tools have become available to the practicing urologist in recent years that endeavor to improve on commonly utilized prostate cancer (PCa) risk-stratification techniques. In this review, we provide an overview of these modalities in the context of active surveillance.

RECENT FINDINGS

Multiparametric MRI (MP-MRI) has a rapidly growing body of evidence that suggests it provides the necessary sensitivity and negative predictive value to rule out clinically significant disease. MRI-guided targeted biopsy has the potential to improve detection of clinically significant cancers and for rebiopsy of patients with continued suspicion for PCa. Prostate-specific antigen isoforms and Prostate Health Index outperform PSA alone and improve risk stratification when combined with the established criteria, but need further prospective studies using template and MRI-targeted biopsies. Urinary biomarkers tend to fall short in predicting adverse pathology when used alone, but improve risk stratification when used in conjunction and with the established criteria. Finally, tissue biomarkers and gene assays allow patient-specific molecular and genetic characterization of cancer phenotype, showing significant promise in predicting adverse pathology, and in some cases have already been incorporated into and altered clinical practice.

SUMMARY

These novel modalities show remarkable promise in improving the risk stratification of patients with PCa, and as the body of evidence grows will likely become incorporated into major oncologic guidelines and standard urologic practice. Further prospective clinical studies are needed, as well as analysis of cost-effectiveness.

Transurethral Resection of the Prostate Biopsy of Suspected Anterior Prostate Cancers Identified by Multiparametric Magnetic Resonance Imaging: A Pilot Study of a Novel Technique

OBJECTIVE

To describe a novel biopsy technique that involves performing a cognitively directed transurethral resection of the prostate (TURP) to diagnose suspected anterior prostate cancers (APCs) detected by multiparametric magnetic resonance imaging (mpMRI) in patients with prior negative transrectal ultrasound (TRUS)-guided biopsies.

METHODS

This is a prospective study in which participants aged 50-75 were offered inclusion if they had an elevated prostate-specific antigen level, a lesion suspicious for APC on mpMRI, and at least one prior negative TRUS-guided prostate biopsy. Prostatic mpMRI was acquired with a 3-Tesla machine without endorectal coil. Preoperative review of the mpMRI images was used to target the suspected APC on TURP biopsy. The primary outcome was the detection rate of clinically significant prostate cancer, defined as the presence of any Gleason pattern ≥ 4 in the specimen. Secondary outcomes included biopsy-related complications including 30-day readmissions.

RESULTS

A total of 16 consecutive participants were enrolled. Median age was 64 years, median prostate-specific antigen was 12.4 ng/mL, and participants had a median of 2 prior negative TRUS-guided biopsies. Thirteen (81.3%) participants had clinically significant APCs detected by TURP biopsy. One participant was readmitted within 30-days postprocedure for continuous bladder irrigation. Seven participants (43.8%) underwent radical prostatectomy that confirmed clinically significant disease in all 7 participants.

CONCLUSION

Among participants with anterior prostate lesions on mpMRI and prior negative TRUS-guided biopsy, TURP biopsy does detect some clinically significant cancers. This study serves as a proof of concept and further comparative trials are needed prior to widespread adoption.

Whole-Tumor Quantitative Apparent Diffusion Coefficient Histogram and Texture Analysis to Predict Gleason Score Upgrading in Intermediate-Risk 3 + 4 = 7 Prostate Cancer

OBJECTIVE

The objective of our study was to evaluate whole-lesion quantitative apparent diffusion coefficient (ADC) for the prediction of Gleason score (GS) upgrading in 3 + 4 = 7 prostate cancer.

MATERIALS AND METHODS

Fifty-four patients with GS 3 + 4 = 7 prostate cancer diagnosed at systematic transrectal ultrasound (TRUS)-guided biopsy underwent 3-T MRI and radical prostatectomy (RP) between 2012 and 2014. A blinded radiologist contoured dominant tumors on ADC maps using histopathologic correlation. The whole-lesion mean ADC, ADC ratio (normalized to peripheral zone), ADC histogram, and texture analysis were compared between tumors with GS upgrading and those without GS upgrading using multivariate ROC analyses and logistic regression modeling.

RESULTS

Tumors were upgraded to GS 4 + 3 = 7 after RP in 26% (n = 14) of the 54 patients, and tumors were downgraded after RP in none of the patients. The mean ADC, ADC ratio, 10th-centile ADC, 25th-centile ADC, and 50th-centile ADC were similar between patients with GS 3 + 4 = 7 tumors (0.99 ± 0.22, 0.58 ± 0.15, 0.77 ± 0.31, 0.94 ± 0.28, and 1.15 ± 0.24, respectively) and patients with upgraded GS 4 + 3 = 7 tumors (1.02 ± 0.18, 0.55 ± 0.11, 0.71 ± 0.26, 0.89 ± 0.20, and 1.11 ± 0.16) (p > 0.05). Regression models combining texture features improved the prediction of GS upgrading. The combination of kurtosis, entropy, and skewness yielded an AUC of 0.76 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 73%. The combination of kurtosis, heterogeneity, entropy, and skewness yielded an AUC of 0.77 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 78%.

CONCLUSION

In this study, whole-lesion mean ADC, ADC ratio, and ADC histogram analysis were not predictive of pathologic upgrading of GS 3 + 4 = 7 prostate cancer after RP. ADC texture analysis improved accuracy.

Active Surveillance of Prostate Cancer: Use, Outcomes, Imaging, and Diagnostic Tools

Active surveillance (AS) has emerged as a standard management option for men with very low-risk and low-risk prostate cancer, and contemporary data indicate that use of AS is increasing in the United States and abroad. In the favorable-risk population, reports from multiple prospective cohorts indicate a less than 1% likelihood of metastatic disease and prostate cancer-specific mortality over intermediate-term follow-up (median 5-6 years). Higher-risk men participating in AS appear to be at increased risk of adverse outcomes, but these populations have not been adequately studied to this point. Although monitoring on AS largely relies on serial prostate biopsy, a procedure associated with considerable morbidity, there is a need for improved diagnostic tools for patient selection and monitoring. Revisions from the 2014 International Society of Urologic Pathology consensus conference have yielded a more intuitive reporting system and detailed reporting of low-intermediate grade tumors, which should facilitate the practice of AS. Meanwhile, emerging modalities such as multiparametric magnetic resonance imaging and tissue-based molecular testing have shown prognostic value in some populations. At this time, however, these instruments have not been sufficiently studied to consider their routine, standardized use in the AS setting. Future studies should seek to identify those platforms most informative in the AS population and propose a strategy by which promising diagnostic tools can be safely and efficiently incorporated into clinical practice.

Combined Biparametric Prostate Magnetic Resonance Imaging and Prostate-specific Antigen in the Detection of Prostate Cancer: A Validation Study in a Biopsy-naive Patient Population

OBJECTIVE

To validate the use of biparametric (T2- and diffusion-weighted) magnetic resonance imaging (B-MRI) and prostate-specific antigen (PSA) or PSA density (PSAD) in a biopsy-naive cohort at risk for prostate cancer (PCa).

METHODS

All patients (n = 59) underwent PSA screening and digital rectal exam prior to a B-MRI followed by MRI or transrectal ultrasound fusion-guided targeted biopsy. Previously reported composite formulas incorporating screen positive lesions (SPL) on B-MRI and PSA or PSAD were developed to maximize PCa detection. For PSA, a patient was considered screen positive if PSA level + 6 × (the number of SPL) >14. For PSAD, screening was positive if PSAD × 14 + (the number of SPL) >4.25. These schemes were employed in this new test set to validate the initial formulas. Performance assessment of these formulas was determined for all cancer detection and for tumors with Gleason ≥3 + 4.

RESULTS

Screen positive lesions on B-MRI had the highest sensitivity (95.5%) and negative predictive value of 71.4% compared with PSA and PSAD. B-MRI significantly improved sensitivity (43.2-72.7%, P = .0002) when combined with PSAD. The negative predictive value of PSA increased with B-MRI, achieving 91.7% for B-MRI and PSA for Gleason ≥3 + 4. Overall accuracies of the composite equations were 81.4% (B-MRI and PSA) and 78.0% (B-MRI and PSAD).

CONCLUSION

Validation with a biopsy-naive cohort demonstrates the parameter SPL performed better than PSA or PSAD alone in accurately detecting PCa. The combined use of B-MRI, PSA, and PSAD resulted in improved accuracy for detecting clinically significant PCa.

Comparison of Multiparametric MRI Scoring Systems and the Impact on Cancer Detection in Patients Undergoing MR US Fusion Guided Prostate Biopsies

Introduction

Multiple scoring systems have been proposed for prostate MRI reporting. We sought to review the clinical impact of the new Prostate Imaging Reporting and Data System v2 (PI-RADS) and compare those results to our proposed Simplified Qualitative System (SQS) score with respect to detection of prostate cancers and clinically significant prostate cancers.

Methods

All patients who underwent multiparametric prostate MRI (mpMRI) had their images interpreted using PI-RADS v1 and SQS score. PI-RADS v2 was calculated from prospectively collected data points. Patients with positive mpMRIs were then referred by their urologists for enrollment in an IRB-approved prospective phase III trial of mpMRI-Ultrasound (MR/TRUS) fusion biopsy of suspicious lesions. Standard 12-core biopsy was performed at the same setting. Clinical data were collected prospectively.

Results

1060 patients were imaged using mpMRI at our institution during the study period. 341 participants were then referred to the trial. 312 participants underwent MR/TRUS fusion biopsy of 452 lesions and were included in the analysis. 202 participants had biopsy-proven cancer (64.7%) and 206 (45.6%) lesions were positive for cancer. Distribution of cancer detected at each score produced a Gaussian distribution for SQS while PI-RADS demonstrates a negatively skewed curve with 82.1% of cases being scored as a 4 or 5. Patient-level data demonstrated AUC of 0.702 (95% CI 0.65 to 0.73) for PI-RADS and 0.762 (95% CI 0.72 to 0.81) for SQS (p< 0.0001) with respect to the detection of prostate cancer. The analysis for clinically significant prostate cancer at a per lesion level resulted in an AUC of 0.725 (95% CI 0.69 to 0.76) and 0.829 (95% CI 0.79 to 0.87) for the PI-RADS and SQS score, respectively (p< 0.0001).

Conclusions

mpMRI is a useful tool in the workup of patients at risk for prostate cancer, and serves as a platform to guide further evaluation with MR/TRUS fusion biopsy. SQS score provided a more normal distribution of scores and yielded a higher AUC than PI-RADS v2. However until our findings are validated, we recommend reporting of detailed sequence-specific findings. This will allow for prospectively collected data to be utilized in determining the impact of ongoing changes to these scoring systems as our understanding of mpMRI interpretation evolves.

PI-RADS version 2: what you need to know

Prostate cancer is the second most prevalent cancer in men worldwide and its incidence is expected to double by 2030. Multi-parametric magnetic resonance imaging (MRI) incorporating anatomical and functional imaging has now been validated as a means of detecting and characterising prostate tumours and can aid in risk stratification and treatment selection. The European Society of Urogenital Radiology (ESUR) in 2012 established the Prostate Imaging-Reporting and Data System (PI-RADS) guidelines aimed at standardising the acquisition, interpretation and reporting of prostate MRI. Subsequent experience and technical developments have highlighted some limitations, and a joint steering committee formed by the American College of Radiology, ESUR, and the AdMeTech Foundation have recently announced an updated version of the proposals. We summarise the main proposals of PI-RADS version 2, explore the evidence behind the recommendations, and highlight key differences for the benefit of those already familiar with the original.

Natural history of small index lesions suspicious for prostate cancer on multiparametric MRI: recommendations for interval imaging follow-up

PURPOSE

We aimed to determine the natural history of small index lesions identified on multiparametric-magnetic resonance imaging (MP-MRI) of the prostate by evaluating lesion-specific pathology and growth on serial MP-MRI.

MATERIALS AND METHODS

We performed a retrospective review of 153 patients who underwent a minimum of two MP-MRI sessions, on an institutional review board-approved protocol. Index lesion is defined as the lesion(s) with the highest cancer suspicion score based on initial MP-MRI of a patient, irrespective of size. Two study cohorts were identified: (1) patients with no index lesion or index lesion(s) ≤7 mm and (2) a subset with no index lesion or index lesion(s) ≤5 mm. Pathological analysis of the index lesions was performed following magnetic resonance/ultrasound fusion-guided biopsy. Growth rate of the lesions was calculated based on MP-MRI follow-up.

RESULTS

Patients with small index lesions measuring ≤7 mm (n=42) or a subset with lesions ≤5 mm (n=20) demonstrated either benign findings (86.2% and 87.5%, respectively) or low grade Gleason 6 prostate cancer (13.8% and 12.5%, respectively) on lesion-specific targeted biopsies. These lesions demonstrated no significant change in size (P = 0.93 and P = 0.36) over a mean imaging period of 2.31±1.56 years and 2.40±1.77 years for ≤7 mm and ≤5 mm index lesion thresholds, respectively. These findings held true on subset analyses of patients who had a minimum of two-year interval follow-up with MP-MRI.

CONCLUSION

Small index lesions of the prostate are pathologically benign lesions or occasionally low-grade cancers. Slow growth rate of these small index lesions on serial MP-MRI suggests a surveillance interval of at least two years without significant change.

Predicting Pathological Features at Radical Prostatectomy in Patients with Prostate Cancer Eligible for Active Surveillance by Multiparametric Magnetic Resonance Imaging

PURPOSE

The aim of this study was to investigate the prognostic performance of multiparametric magnetic resonance imaging (mpMRI) and Prostate Imaging Reporting and Data System (PIRADS) score in predicting pathologic features in a cohort of patients eligible for active surveillance who underwent radical prostatectomy.

METHODS

A total of 223 patients who fulfilled the criteria for "Prostate Cancer Research International: Active Surveillance", were included. Mp-1.5 Tesla MRI examination staging with endorectal coil was performed at least 6-8 weeks after TRUS-guided biopsy. In all patients, the likelihood of the presence of cancer was assigned using PIRADS score between 1 and 5. Outcomes of interest were: Gleason score upgrading, extra capsular extension (ECE), unfavorable prognosis (occurrence of both upgrading and ECE), large tumor volume (≥ 0.5 ml), and seminal vesicle invasion (SVI). Receiver Operating Characteristic (ROC) curves and Decision Curve Analyses (DCA) were performed for models with and without inclusion of PIRADS score.

RESULTS

Multivariate analysis demonstrated the association of PIRADS score with upgrading (P < 0.0001), ECE (P < 0.0001), unfavorable prognosis (P < 0.0001), and large tumor volume (P = 0.002). ROC curves and DCA showed that models including PIRADS score resulted in greater net benefit for almost all the outcomes of interest, with the only exception of SVI.

CONCLUSIONS

mpMRI and PIRADS scoring are feasible tools in clinical setting and could be used as decision-support systems for a more accurate selection of patients eligible for AS.

Clinical Case Discussion: Intermediate-risk Prostate Cancer: The Case for Active Surveillance

Active surveillance offers men the opportunity to defer immediate local treatment of low risk prostate cancer while preserving a highly functional quality of life. Novel biomarkers and imaging technology will enable physicians to better identify ideal candidates for this approach beyond traditional clinical characteristics.

Diagnosis of Extracapsular Extension of Prostate Cancer on Prostate MRI: Impact of Second-Opinion Readings by Subspecialized Genitourinary Oncologic Radiologists

OBJECTIVE

The purpose of this article is to investigate the added value of second-opinion evaluation of prostate MRI by subspecialized genitourinary oncologic radiologists for the assessment of extracapsular extension (ECE) of prostate cancer.

MATERIALS AND METHODS

We performed a retrospective evaluation of initial and second-opinion radiology reports of 76 patients who underwent MRI of the prostate before prostatectomy for histologically proven prostate cancer. Initial outside reports and second-opinion reports were unpaired and reviewed in random order by a urologist who was blinded to patients' clinical details and histopathologic data. Histopathologic analysis of the prostatectomy specimen served as the reference standard.

RESULTS

Among cases with diagnostic-quality images available (71/76; 93%), disagreement between the initial report and the second-opinion report was observed in 30% of cases (21/71; κ = 0.35); in 18 of these 21 cases (86%), histopathologic analysis proved that the second-opinion report was correct. The second-opinion interpretations had statistically significantly higher sensitivity (66% vs 24%; p < 0.0001) than did the initial reports, whereas there was no statistically significant difference in specificity (87% vs 93%; p = 0.317). On ROC curve analysis, the second-opinion reports yielded a statistically significantly higher AUC for the detection of ECE (0.80 vs 0.65; p = 0.004).

CONCLUSION

The reinterpretation of prostate MRI examinations by subspecialized genitourinary oncologic radiologists improved the detection of ECE of prostate cancer.

Targeted prostate biopsy: value of multiparametric magnetic resonance imaging in detection of localized cancer

Prostate cancer is the second most common cancer in men, with 1.1 million new cases worldwide reported by the World Health Organization in one recent year. Transrectal ultrasound (TRUS)-guided biopsy has been used for the diagnosis of prostate cancer for over 2 decades, but the technique is usually blind to cancer location. Moreover, the false negative rate of TRUS biopsy has been reported to be as high as 47%. Multiparametric magnetic resonance imaging (mp-MRI) includes T1- and T2-weighted imaging as well as dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI). mp-MRI is a major advance in the imaging of prostate cancer, enabling targeted biopsy of suspicious lesions. Evolving targeted biopsy techniques-including direct in-bore biopsy, cognitive fusion and software-based MRI-ultrasound (MRI-US) fusion-have led to a several-fold improvement in cancer detection compared to the earlier method. Importantly, the detection of clinically significant cancers has been greatly facilitated by targeting, compared to systematic biopsy alone. Targeted biopsy via MRI-US fusion may dramatically alter the way prostate cancer is diagnosed and managed.

Multiparametric-MRI in diagnosis of prostate cancer

Multiparametric-magnetic resonance imaging (mp-MRI) has shown promising results in diagnosis, localization, risk stratification and staging of clinically significant prostate cancer. It has also opened up opportunities for focal treatment of prostate cancer. Combinations of T2-weighted imaging, diffusion imaging, perfusion (dynamic contrast-enhanced imaging) and spectroscopic imaging have been used in mp-MRI assessment of prostate cancer, but T2 morphologic assessment and functional assessment by diffusion imaging remains the mainstay for prostate cancer diagnosis on mp-MRI. Because assessment on mp-MRI can be subjective, use of the newly developed standardized reporting Prostate Imaging and Reporting Archiving Data System scoring system and education of specialist radiologists are essential for accurate interpretation. This review focuses on the present status of mp-MRI in prostate cancer and its evolving role in the management of prostate cancer.

Magnetic Resonance-Guided Prostate Biopsy

The optimal strategy for prostate cancer diagnosis is to avoid overdiagnosis, defined as diagnosis of clinically insignificant disease, and undersampling of the gland, which leads to missing clinically significant disease. Targeted prostate biopsy is a potential solution for decreasing the rate of both overdiagnosis and undersampling of prostate cancer. We focus here on different techniques for targeting prostate lesions identified on multiparametric MR imaging and review different clinical settings in which MR imaging-targeted prostate biopsies are performed.

Impact of an Information Technology-Enabled Initiative on the Quality of Prostate Multiparametric MRI Reports

RATIONALE AND OBJECTIVES

Assess the impact of implementing a structured report template and a computer-aided diagnosis (CAD) tool on the quality of prostate multiparametric magnetic resonance imaging (mp-MRI) reports.

MATERIALS AND METHODS

Institutional Review Board approval was obtained for this Health Insurance Portability and Accountability Act-compliant study performed at an academic medical center. The study cohort included all prostate mp-MRI reports (n = 385) finalized 6 months before and after implementation of a structured report template and a CAD tool (collectively the information technology [IT] tools) integrated into the picture archiving and communication system workstation. Primary outcome measure was quality of prostate mp-MRI reports. An expert panel of our institution's subspecialty-trained abdominal radiologists defined prostate mp-MRI report quality as optimal, satisfactory, or unsatisfactory based on documentation of nine variables. Reports were reviewed to extract the predefined quality variables and determine whether the IT tools were used to create each report. Chi-square and Student's t tests were used to compare report quality before and after implementation of IT tools.

RESULTS

The overall proportion of optimal or satisfactory reports increased from 29.8% (47/158) to 53.3% (121/227) (P < .001) after implementing the IT tools. Although the proportion of optimal or satisfactory reports increased among reports generated using at least one of the IT tools (47/158 = [29.8%] vs. 105/161 = [65.2%]; P < .001), there was no change in quality among reports generated without use of the IT tools (47/158 = [29.8%] vs. 16/66 = [24.2%]; P = .404).

CONCLUSIONS

The use of a structured template and CAD tool improved the quality of prostate mp-MRI reports compared to free-text report format and subjective measurement of contrast enhancement kinetic curve.

Multiparametric magnetic resonance imaging for prostate cancer: A review and update for urologists

Recently, imaging of prostate cancer has greatly advanced since the introduction of multiparametric magnetic resonance imaging (mpMRI). mpMRI consists of T2-weighted sequences combined with several functional sequences including diffusion-weighted imaging, dynamic contrast-enhanced imaging, and/or magnetic resonance spectroscopy imaging. Interest has been growing in mpMRI because no single MRI sequence adequately detects and characterizes prostate cancer. During the last decade, the role of mpMRI has been expanded in prostate cancer detection, staging, and targeting or guiding prostate biopsy. Recently, mpMRI has been used to assess prostate cancer aggressiveness and to identify anteriorly located tumors before and during active surveillance. Moreover, recent studies have reported that mpMRI is a reliable imaging modality for detecting local recurrence after radical prostatectomy or external beam radiation therapy. In this regard, some urologic clinical practice guidelines recommended the use of mpMRI in the diagnosis and management of prostate cancer. Because mpMRI is the evolving reference standard imaging modality for prostate cancer, urologists should acquire cutting-edge knowledge about mpMRI. In this article, we review the literature on the use of mpMRI in urologic practice and provide a brief description of techniques. More specifically, we state the role of mpMRI in prostate biopsy, active surveillance, high-risk prostate cancer, and detection of recurrence after radical prostatectomy.

Prostate Cancer: Interobserver Agreement and Accuracy with the Revised Prostate Imaging Reporting and Data System at Multiparametric MR Imaging

PURPOSE

To evaluate accuracy and interobserver variability with the use of the Prostate Imaging Reporting and Data System (PI-RADS) version 2.0 for detection of prostate cancer at multiparametric magnetic resonance (MR) imaging in a biopsy-naïve patient population.

MATERIALS AND METHODS

This retrospective HIPAA-compliant study was approved by the local ethics committee, and written informed consent was obtained from all patients for use of their imaging and histopathologic data in future research studies. In 101 biopsy-naïve patients with elevated prostate-specific antigen levels who underwent multiparametric MR imaging of the prostate and subsequent transrectal ultrasonography (US)-MR imaging fusion-guided biopsy, suspicious lesions detected at multiparametric MR imaging were scored by five readers who were blinded to pathologic results by using to the newly revised PI-RADS and the scoring system developed in-house. Interobserver agreement was evaluated by using κ statistics, and the correlation of pathologic results with each of the two scoring systems was evaluated by using the Kendall τ correlation coefficient.

RESULTS

Specimens of 162 lesions in 94 patients were sampled by means of transrectal US-MR imaging fusion biopsy. Results for 87 (54%) lesions were positive for prostate cancer. Kendall τ values with the PI-RADS and the in-house-developed scoring system, respectively, at T2-weighted MR imaging in the peripheral zone were 0.51 and 0.17 and in the transitional zone, 0.45 and -0.11; at diffusion-weighted MR imaging, 0.42 and 0.28; at dynamic contrast material-enhanced MR imaging, 0.23 and 0.24, and overall suspicion scores were 0.42 and 0.49. Median κ scores among all possible pairs of readers for PI-RADS and the in-house-developed scoring system, respectively, for T2-weighted MR images in the peripheral zone were 0.47 and 0.15; transitional zone, 0.37 and 0.07; diffusion-weighted MR imaging, 0.41 and 0.57; dynamic contrast-enhanced MR imaging, 0.48 and 0.41; and overall suspicion scores, 0.46 and 0.55.

CONCLUSION

Use of the revised PI-RADS provides moderately reproducible MR imaging scores for detection of clinically relevant disease.

Abnormal findings on multiparametric prostate magnetic resonance imaging predict subsequent biopsy upgrade in patients with low risk prostate cancer managed with active surveillance

PURPOSE

To determine the ability of multiparametric MR imaging to predict disease progression in patients with prostate cancer managed by active surveillance.

METHODS

Sixty-four men with biopsy-proven prostate cancer managed by active surveillance were included in this HIPPA compliant, IRB approved study. We reviewed baseline MR imaging scans for the presence of a suspicious findings on T2-weighted imaging, MR spectroscopic imaging (MRSI), and diffusion-weighted MR imaging (DWI). The Gleason grades at subsequent biopsy were recorded. A Cox proportional hazard model was used to determine the predictive value of MR imaging for Gleason grades, and the model performance was described using Harrell's C concordance statistic and 95% confidence intervals (CIs).

RESULTS

The Cox model that incorporated T2-weighted MR imaging, DWI, and MRSI showed that only T2-weighted MR imaging and DWI are independent predictors of biopsy upgrade (T2; HR = 2.46; 95% CI 1.36-4.46; P = 0.003-diffusion; HR = 2.76; 95% CI 1.13-6.71; P = 0.03; c statistic = 67.7%; 95% CI 61.1-74.3). There was an increasing rate of Gleason score upgrade with a greater number of concordant findings on multiple MR sequences (HR = 2.49; 95% CI 1.72-3.62; P < 0.001).

CONCLUSIONS

Abnormal results on multiparametric prostate MRI confer an increased risk for Gleason score upgrade at subsequent biopsy in men with localized prostate cancer managed by active surveillance. These results may be of help in appropriately selecting candidates for active surveillance.

A novel technique using three-dimensionally documented biopsy mapping allows precise re-visiting of prostate cancer foci with serial surveillance of cell cycle progression gene panel

BACKGROUND

Conventional systematic biopsy has the shortcoming of sampling error and reveals "no evidence of cancer" with a rate of >50% on active surveillance (AS). The objective of this study is to report our initial experience of applying a 3D-documented biopsy-mapping technology to precisely re-visit geographically documented low-risk prostate cancer and to perform serial analysis of cell-cycle-progression (CCP) gene-panel.

METHODS

Over a period of 40 months (1/2010-4/2013), the 3D-biopsy-mapping technique, in which the spatial location of biopsy-trajectory was digitally recorded (Koelis), was carried out. A pair of diagnostic (1st-look) and surveillance (2nd-look) biopsy were performed per subject (n = 25), with median interval of 12 months. The documented biopsy-trajectory was used as a target to guide the re-visiting biopsy from the documented cancer focus, as well as the targeted field-biopsy from the un-sampled prostatic field adjacent to negative diagnostic biopsies. The accuracy of re-visiting biopsy and biopsy-derived CCP signatures were evaluated in the pair of the serial biopsy-cores.

RESULTS

The 1st-look-biopsy revealed a total of 43 cancer lesions (1.7 per patient). The accuracy of re-visiting cancer was 86% (37/43) per lesion, 76% (65/86) per core, and 80% (20/25) per patient. This technology also provided an opportunity for 3D-targeted field-biopsy in order to potentially minimize sampling errors. The CCP gene-panel of the 1st-look (-0.59) versus 2nd-look (-0.37) samples had no significant difference (P = 0.4); which suggested consistency in the molecular signature of the known cancer foci during the short-time interval of median 12 months. Any change in CCP of the same cancer foci would be likely due to change in sampling location from the less to more significant portion in the cancer foci rather than true molecular progression. The study limitations include a small number of the patients.

CONCLUSION

The 3D-documented biopsy-mapping technology achieved an encouraging re-sampling accuracy of 86% from the known prostate cancer foci, allowing the serial analysis of biopsy-derived CCP signatures.

Role for (11)C-choline PET in active surveillance of prostate cancer

INTRODUCTION

Active surveillance (AS) is an increasingly popular management strategy for men diagnosed with low-risk indolent prostate cancer. Current tests (prostate-specific antigen [PSA], clinical staging, and prostate biopsies) to monitor indolent disease lack accuracy. (11)C-choline positron emission tomography (PET) has excellent detection rates in local and distant recurrence of prostate cancer. We examine (11)C-choline PET for identifying aggressive prostate cancer warranting treatment in the AS setting.

METHODS

In total, 24 patients on AS had clinical assessment and PSA testing every 6 months and (11)C-choline PET and prostate biopsies annually. The sensitivity and specificity to identify prostate cancer and progressive disease (PD) were calculated for each (11)C-choline PET scan.

RESULTS

In total, 62 biopsy-paired, serial (11)C-choline PET scans were analyzed using a series of standard uptake value-maximum (SUVmax) cut-off thresholds. During follow-up (mean 25.3 months), 11 of the 24 low-risk prostate cancer patients developed PD and received definitive treatment. The prostate cancer detection rate with (11)C-choline PET had moderate sensitivity (72.1%), but low specificity (45.0%). PD prediction from baseline (11)C-choline PET had satisfactory sensitivity (81.8%), but low specificity (38.5%). The addition of clinical parameters to the baseline (11)C-choline PET improved specificity (69.2%), with a slight reduction in sensitivity (72.7%) for PD prediction.

CONCLUSIONS

Addition of (11)C-choline PET imaging during AS may help to identify aggressive disease earlier than traditional methods. However, (11)C-choline PET alone has low specificity due to overlap of SUV values with benign pathologies. Triaging low-risk prostate cancer patients into AS versus therapy will require further optimization of PET protocols or consideration of alternative strategies (i.e., magnetic resonance imaging, biomarkers).

Use of serial multiparametric magnetic resonance imaging in the management of patients with prostate cancer on active surveillance

INTRODUCTION

We evaluated the performance of multiparametric prostate magnetic resonance imaging (mp-MRI) and MRI/transrectal ultrasound (TRUS) fusion-guided biopsy (FB) for monitoring patients with prostate cancer on active surveillance (AS).

MATERIALS AND METHODS

Patients undergoing mp-MRI and FB of target lesions identified on mp-MRI between August 2007 and August 2014 were reviewed. Patients meeting AS criteria (Clinical stage T1c, Gleason grade ≤ 6, prostate-specific antigen density ≤ 0.15, tumor involving ≤ 2 cores, and ≤ 50% involvement of any single core) based on extended sextant 12-core TRUS biopsy (systematic biopsy [SB]) were included. They were followed with subsequent 12-core biopsy as well as mp-MRI and MRI/TRUS fusion biopsy at follow-up visits until Gleason score progression (Gleason ≥ 7 in either 12-core or MRI/TRUS fusion biopsy). We evaluated whether progression seen on mp-MRI (defined as an increase in suspicion level, largest lesion diameter, or number of lesions) was predictive of Gleason score progression.

RESULTS

Of 152 patients meeting AS criteria on initial SB (mean age of 61.4 years and mean prostate-specific antigen level of 5.26 ng/ml), 34 (22.4%) had Gleason score ≥ 7 on confirmatory SB/FB. Of the 118 remaining patients, 58 chose AS and had at least 1 subsequent mp-MRI with SB/FB (median follow-up = 16.1 months). Gleason progression was subsequently documented in 17 (29%) of these men, in all cases to Gleason 3+4. The positive predictive value and negative predictive value of mp-MRI for Gleason progression was 53% (95% CI: 28%-77%) and 80% (95% CI: 65%-91%), respectively. The sensitivity and specificity of mp-MRI for increase in Gleason were also 53% and 80%, respectively. The number needed to biopsy to detect 1 Gleason progression was 8.74 for SB vs. 2.9 for FB.

CONCLUSIONS

Stable findings on mp-MRI are associated with Gleason score stability. mp-MRI appears promising as a useful aid for reducing the number of biopsies in the management of patients on AS. A prospective evaluation of mp-MRI as a screen to reduce biopsies in the follow-up of men on AS appears warranted.

Diagnostic value of biparametric magnetic resonance imaging (MRI) as an adjunct to prostate-specific antigen (PSA)-based detection of prostate cancer in men without prior biopsies

OBJECTIVES

To determine the diagnostic yield of analysing biparametric (T2- and diffusion-weighted) magnetic resonance imaging (B-MRI) for prostate cancer detection compared with standard digital rectal examination (DRE) and prostate-specific antigen (PSA)-based screening.

PATIENTS AND METHODS

Review of patients who were enrolled in a trial to undergo multiparametric-prostate (MP)-MRI and MR/ultrasound fusion-guided prostate biopsy at our institution identified 143 men who underwent MP-MRI in addition to standard DRE and PSA-based prostate cancer screening before any prostate biopsy. Patient demographics, DRE staging, PSA level, PSA density (PSAD), and B-MRI findings were assessed for association with prostate cancer detection on biopsy.

RESULTS

Men with detected prostate cancer tended to be older, with a higher PSA level, higher PSAD, and more screen-positive lesions (SPL) on B-MRI. B-MRI performed well for the detection of prostate cancer with an area under the curve (AUC) of 0.80 (compared with 0.66 and 0.74 for PSA level and PSAD, respectively). We derived combined PSA and MRI-based formulas for detection of prostate cancer with optimised thresholds. (i) for PSA and B-MRI: PSA level + 6 x (the number of SPL) > 14 and (ii) for PSAD and B-MRI: 14 × (PSAD) + (the number of SPL) >4.25. AUC for equations 1 and 2 were 0.83 and 0.87 and overall accuracy of prostate cancer detection was 79% in both models.

CONCLUSIONS

The number of lesions positive on B-MRI outperforms PSA alone in detection of prostate cancer. Furthermore, this imaging criteria coupled as an adjunct with PSA level and PSAD, provides even more accuracy in detecting clinically significant prostate cancer.

The role of image guided biopsy targeting in patients with atypical small acinar proliferation

PURPOSE

Men diagnosed with atypical small acinar proliferation are counseled to undergo early rebiopsy because the risk of prostate cancer is high. However, random rebiopsies may not resample areas of concern. Magnetic resonance imaging/transrectal ultrasound fusion guided biopsy offers an opportunity to accurately target and later retarget specific areas in the prostate. We describe the ability of magnetic resonance imaging/transrectal ultrasound fusion guided prostate biopsy to detect prostate cancer in areas with an initial diagnosis of atypical small acinar proliferation.

MATERIALS AND METHODS

Multiparametric magnetic resonance imaging of the prostate and magnetic resonance imaging/transrectal ultrasound fusion guided biopsy were performed in 1,028 patients from March 2007 to February 2014. Of the men 20 met the stringent study inclusion criteria, which were no prostate cancer history, index biopsy showing at least 1 core of atypical small acinar proliferation with benign glands in all remaining cores and fusion targeted rebiopsy with at least 1 targeted core directly resampling an area of the prostate that previously contained atypical small acinar proliferation.

RESULTS

At index biopsy median age of the 20 patients was 60 years (IQR 57-64) and median prostate specific antigen was 5.92 ng/ml (IQR 3.34-7.48). At fusion targeted rebiopsy at a median of 11.6 months 5 of 20 patients (25%, 95% CI 6.02-43.98) were diagnosed with primary Gleason grade 3, low volume prostate cancer. On fusion rebiopsy cores that directly retargeted areas of previous atypical small acinar proliferation detected the highest tumor burden.

CONCLUSIONS

When magnetic resonance imaging/transrectal ultrasound fusion guided biopsy detects isolated atypical small acinar proliferation on index biopsy, early rebiopsy is unlikely to detect clinically significant prostate cancer. Cores that retarget areas of previous atypical small acinar proliferation are more effective than random rebiopsy cores.

Comparison of MR/ultrasound fusion-guided biopsy with ultrasound-guided biopsy for the diagnosis of prostate cancer

IMPORTANCE

Targeted magnetic resonance (MR)/ultrasound fusion prostate biopsy has been shown to detect prostate cancer. The implications of targeted biopsy alone vs standard extended-sextant biopsy or the 2 modalities combined are not well understood.

OBJECTIVE

To assess targeted vs standard biopsy and the 2 approaches combined for the diagnosis of intermediate- to high-risk prostate cancer.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study of 1003 men undergoing both targeted and standard biopsy concurrently from 2007 through 2014 at the National Cancer Institute in the United States. Patients were referred for elevated level of prostate-specific antigen (PSA) or abnormal digital rectal examination results, often with prior negative biopsy results. Risk categorization was compared among targeted and standard biopsy and, when available, whole-gland pathology after prostatectomy as the "gold standard."

INTERVENTIONS

Patients underwent multiparametric prostate magnetic resonance imaging to identify regions of prostate cancer suspicion followed by targeted MR/ultrasound fusion biopsy and concurrent standard biopsy.

MAIN OUTCOMES AND MEASURES

The primary objective was to compare targeted and standard biopsy approaches for detection of high-risk prostate cancer (Gleason score ≥ 4 + 3); secondary end points focused on detection of low-risk prostate cancer (Gleason score 3 + 3 or low-volume 3 + 4) and the biopsy ability to predict whole-gland pathology at prostatectomy.

RESULTS

Targeted MR/ultrasound fusion biopsy diagnosed 461 prostate cancer cases, and standard biopsy diagnosed 469 cases. There was exact agreement between targeted and standard biopsy in 690 men (69%) undergoing biopsy. Targeted biopsy diagnosed 30% more high-risk cancers vs standard biopsy (173 vs 122 cases, P < .001) and 17% fewer low-risk cancers (213 vs 258 cases, P < .001). When standard biopsy cores were combined with the targeted approach, an additional 103 cases (22%) of mostly low-risk prostate cancer were diagnosed (83% low risk, 12% intermediate risk, and 5% high risk). The predictive ability of targeted biopsy for differentiating low-risk from intermediate- and high-risk disease in 170 men with whole-gland pathology after prostatectomy was greater than that of standard biopsy or the 2 approaches combined (area under the curve, 0.73, 0.59, and 0.67, respectively; P < .05 for all comparisons).

CONCLUSIONS AND RELEVANCE

Among men undergoing biopsy for suspected prostate cancer, targeted MR/ultrasound fusion biopsy, compared with standard extended-sextant ultrasound-guided biopsy, was associated with increased detection of high-risk prostate cancer and decreased detection of low-risk prostate cancer. Future studies will be needed to assess the ultimate clinical implications of targeted biopsy.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00102544.

Clinical implications of a multiparametric magnetic resonance imaging based nomogram applied to prostate cancer active surveillance

PURPOSE

Multiparametric magnetic resonance imaging may be beneficial in the search for rational ways to decrease prostate cancer intervention in patients on active surveillance. We applied a previously generated nomogram based on multiparametric magnetic resonance imaging to predict active surveillance eligibility based on repeat biopsy outcomes.

MATERIALS AND METHODS

We reviewed the records of 85 patients who met active surveillance criteria at study entry based on initial biopsy and who then underwent 3.0 Tesla multiparametric magnetic resonance imaging with subsequent magnetic resonance imaging/ultrasound fusion guided prostate biopsy between 2007 and 2012. We assessed the accuracy of a previously published nomogram in patients on active surveillance before confirmatory biopsy. For each cutoff we determined the number of biopsies avoided (ie reliance on magnetic resonance imaging alone without rebiopsy) over the full range of nomogram cutoffs.

RESULTS

We assessed the performance of the multiparametric magnetic resonance imaging active surveillance nomogram based on a decision to perform biopsy at various nomogram generated probabilities. Based on cutoff probabilities of 19% to 32% on the nomogram the number of patients who could be spared repeat biopsy was 27% to 68% of the active surveillance cohort. The sensitivity of the test in this interval was 97% to 71% and negative predictive value was 91% to 81%.

CONCLUSIONS

Multiparametric magnetic resonance imaging based nomograms may reasonably decrease the number of repeat biopsies in patients on active surveillance by as much as 68%. Analysis over the full range of nomogram generated probabilities allows patient and caregiver preference based decision making on the risk assumed for the benefit of fewer repeat biopsies.

Imaging biomarkers in prostate cancer: role of PET/CT and MRI

Prostate-specific antigen (PSA) is currently the most widely used biomarker of prostate cancer (PCa). PSA suggests the presence of primary tumour and disease relapse after treatment, but it is not able to provide a clear distinction between locoregional and distant disease. Molecular and functional imaging, that are able to provide a detailed and comprehensive overview of PCa extension, are more reliable tools for primary tumour detection and disease extension assessment both in staging and restaging. In the present review we evaluate the role of PET/CT and MRI in the diagnosis, staging and restaging of PCa, and the use of these imaging modalities in prognosis, treatment planning and response assessment. Innovative imaging strategies including new radiotracers and hybrid scanners such as PET/MRI are also discussed.

Novel technique for characterizing prostate cancer utilizing MRI restriction spectrum imaging: proof of principle and initial clinical experience with extraprostatic extension

BACKGROUND

Standard magnetic resonance imaging (MRI) of the prostate lacks sensitivity in the diagnosis and staging of prostate cancer (PCa). To improve the operating characteristics of prostate MRI in the detection and characterization of PCa, we developed a novel, enhanced MRI diffusion technique using restriction spectrum imaging (RSI-MRI).

METHODS

We compared the efficacy of our novel RSI-MRI technique with standard MRI for detecting extraprostatic extension (EPE) among 28 PCa patients who underwent MRI and RSI-MRI prior to radical prostatectomy, 10 with histologically proven pT3 disease. RSI cellularity maps isolating the restricted isotropic water fraction were reconstructed based on all b-values and then standardized across the sample with z-score maps. Distortion correction of the RSI maps was performed using the alternating phase-encode technique.

RESULTS

27 patients were evaluated, excluding one patient where distortion could not be performed. Preoperative standard MRI correctly identified extraprostatic the extension in two of the nine pT3 (22%) patients, whereas RSI-MRI identified EPE in eight of nine (89%) patients. RSI-MRI correctly identified pT2 disease in the remaining 18 patients.

CONCLUSIONS

In this proof of principle study, we conclude that our novel RSI-MRI technology is feasible and shows promise for substantially improving PCa imaging. Further translational studies of prostate RSI-MRI in the diagnosis and staging of PCa are indicated.

The role of 3-tesla diffusion-weighted magnetic resonance imaging in selecting prostate cancer patients for active surveillance

Purpose

Differentiating significant cancer from insignificant cancer is a major challenge in active surveillance (AS) for prostate cancer. We evaluated whether the apparent diffusion coefficient (ADC) grade from 3-T diffusion-weighted magnetic resonance imaging (DW-MRI) is useful to exclude men with unfavorable pathological features from men meeting current AS eligibility criteria.

Methods

Among patients who underwent radical prostatectomy, 117 potential AS candidates defined according to 2013 European Association of Urology guidelines who had undergone preoperative 3-T DW-MRI were included. A blinded uro-radiologist graded the level of suspicion from the ADC map using the Likert scale from 1 to 5. The rate of unfavorable pathological features was evaluated according to ADC grade. Unfavorable pathological features were defined as non–organ-confined disease or pathological Gleason score≥7 (4+3). The associations between unfavorable pathological features and clinical variables including ADC grade (>3 vs. ≤3) were evaluated using logistic regression analysis.

Results

The rates of unfavorable pathological features were 0.0% (0/14), 2.9% (1/34), 5.4% (2/37), 25.0% (6/24), and 37.5% (3/8) from grades 1 to 5 (P=0.002). The predictive accuracy was as high as 0.804. The rates were significantly different between low (≤3, 3.5%) and high (>3, 28.1%, P<0.001) grades. The sensitivity, specificity, and positive and negative predictive values were 75.0%, 78.1%, 28.1%, and 96.5%. ADC grade (odds ratio [OR], 10.696; 95% confidence interval [CI], 2.675–42.773) was significantly associated with unfavorable pathological features, even after adjusting for other variables (OR, 11.274; 95% CI, 2.622–48.471).

Conclusions

ADC grade from 3-T DW-MRI is useful to predict men with unfavorable pathologic features from AS candidates.

Multiparametric MRI for localized prostate cancer: lesion detection and staging

Multiparametric MRI of the prostate combines high-resolution anatomic imaging with functional imaging of alterations in normal tissue caused by neoplastic transformation for the identification and characterization of in situ prostate cancer. Lesion detection relies on a systematic approach to the analysis of both anatomic and functional imaging using established criteria for the delineation of suspicious areas. Staging includes visual and functional analysis of the prostate "capsule" to determine if in situ disease is, in fact, organ-confined, as well as the evaluation of pelvic structures including lymph nodes and bones for the detection of metastasis. Although intertwined, the protocol can be optimized depending on whether lesion detection or staging is of the highest priority.

The role of MRI in prostate cancer active surveillance

Prostate cancer is the most common cancer diagnosis in American men, excluding skin cancer. The clinical behavior of prostate cancer varies from low-grade, slow growing tumors to high-grade aggressive tumors that may ultimately progress to metastases and cause death. Given the high incidence of men diagnosed with prostate cancer, conservative treatment strategies such as active surveillance are critical in the management of prostate cancer to reduce therapeutic complications of radiation therapy or radical prostatectomy. In this review, we will review the role of multiparametric MRI in the selection and follow-up of patients on active surveillance.

How accurate is multiparametric MR imaging in evaluation of prostate cancer volume?

PURPOSE

To assess the factors influencing multiparametric (MP) magnetic resonance (MR) imaging accuracy in estimating prostate cancer histologic volume (Vh).

MATERIALS AND METHODS

A prospective database of 202 patients who underwent MP MR imaging before radical prostatectomy was retrospectively used. Institutional review board approval and informed consent were obtained. Two independent radiologists delineated areas suspicious for cancer on images (T2-weighted, diffusion-weighted, dynamic contrast material-enhanced [DCE] pulse sequences) and scored their degree of suspicion of malignancy by using a five-level Likert score. One pathologist delineated cancers on whole-mount prostatectomy sections and calculated their volume by using digitized planimetry. Volumes of MR true-positive lesions were measured on T2-weighted images (VT2), on ADC maps (VADC), and on DCE images [VDCE]). VT2, VADC, VDCE and the greatest volume determined on images from any of the individual MR pulse sequences (Vmax) were compared with Vh (Bland-Altman analysis). Factors influencing MP MR imaging accuracy, or A, calculated as A = Vmax/Vh, were evaluated using generalized linear mixed models.

RESULTS

For both readers, Vh was significantly underestimated with VT2 (P < .0001, both), VADC (P < .0001, both), and VDCE (P = .02 and P = .003, readers 1 and 2, respectively), but not with Vmax (P = .13 and P = .21, readers 1 and 2, respectively). Mean, 25th percentile, and 75th percentile, respectively, for Vmax accuracy were 0.92, 0.54, and 1.85 for reader 1 and 0.95, 0.57, and 1.77 for reader 2. At generalized linear mixed (multivariate) analysis, tumor Likert score (P < .0001), Gleason score (P = .009), and Vh (P < .0001) significantly influenced Vmax accuracy (both readers). This accuracy was good in tumors with a Gleason score of 7 or higher or a Likert score of 5, with a tendency toward underestimation of Vh; accuracy was poor in small (<0.5 cc) or low-grade (Gleason score ≤6) tumors, with a tendency toward overestimation of Vh.

CONCLUSION

Vh can be estimated by using Vmax in aggressive tumors or in tumors with high Likert scores.

Magnetic resonance imaging in active surveillance of prostate cancer: a systematic review

CONTEXT

There is great interest in using magnetic resonance imaging (MRI) for men on active surveillance for prostate cancer.

OBJECTIVE

To systematically review evidence regarding the use of MRI in men with low- or intermediate-risk prostate cancer suitable for active surveillance.

EVIDENCE ACQUISITION

Ovid Medline and Embase databases were searched for active surveillance, prostate cancer, and MRI from inception until April 25, 2014 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses process. Identified reports were critically appraised according to the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) criteria.

EVIDENCE SYNTHESIS

A lesion on MRI suspicious for prostate cancer (positive MRI) is seen in two-thirds of men otherwise suitable for active surveillance. A positive MRI makes the identification of clinically significant disease at repeat biopsy more likely, especially when biopsies are targeted to suspicious MRI lesions. Radical prostatectomy data show that positive MRI is more likely to be associated with upgrading (Gleason score>3+3) than a negative MRI (43% vs 27%). A positive MRI is not significantly more likely to be associated with upstaging at radical prostatectomy (>T2) than a negative MRI (10% vs 8%). Although MRI is of interest in the monitoring of men on active surveillance, robust data on the use of repeat MRI in active surveillance are lacking. Prospective studies with clear definitions of radiological significance and progression are needed before this approach can be adopted.

CONCLUSIONS

MRI is useful for detection of clinically significant disease at initial assessment of men considering active surveillance. To use MRI as a monitoring tool in surveillance, it will be necessary to define both radiological significance and radiological progression.

PATIENT SUMMARY

This review assesses evidence for the use of magnetic resonance imaging (MRI) in men on active surveillance for prostate cancer. MRI at the start of surveillance can detect clinically significant disease in one-third to half of men. There are few data to assess the use of MRI as a monitoring tool during surveillance, so there is a need to define significant disease on MRI and significant changes over time.

Multiparametric magnetic resonance imaging vs. standard care in men being evaluated for prostate cancer: a randomized study

OBJECTIVES

To assess whether the proportion of men with clinically significant prostate cancer (PCa) is higher among men randomized to multiparametric magnetic resonance imaging (mp-MRI)/biopsy vs. those randomized to transrectal ultrasound (TRUS)-guided biopsy.

METHODS

In total, 1,140 patients with symptoms highly suggestive of PCa were enrolled and divided in 2 groups of 570 patients to follow 2 different diagnostic algorithms. Group A underwent a TRUS-guided random biopsy. Group B underwent an mp-MRI and a TRUS-guided targeted+random biopsy. The accuracy of mp-MRI in the diagnosis of PCa was calculated using prostatectomy as the standard of reference.

RESULTS

In group A, PCa was detected in 215 patients. The remaining 355 patients underwent an mp-MRI: the findings were positive in 208 and unremarkable in 147 patients. After the second random+targeted biopsy, PCa was detected in 186 of the 208 patients. In group B, 440 patients had positive findings on mp-MRI, and PCa was detected in 417 at first biopsy; 130 group B patients had unremarkable findings on both mp-MRI and biopsy. In the 130 group B patients with unremarkable findings on mp-MRI and biopsy, a PCa Gleason score of 6 or precancerous lesions were detected after saturation biopsy. mp-MRI showed an accuracy of 97% for the diagnosis of PCa.

CONCLUSIONS

The proportion of men with clinically significant PCa is higher among those randomized to mp-MRI/biopsy vs. those randomized to TRUS-guided biopsy; moreover, mp-MRI is a very reliable tool to identify patients to schedule in active surveillance.

Role of multiparametric magnetic resonance imaging in the diagnosis of prostate cancer

Prostate cancer is the most common solid-organ malignancy among American men. It is currently most commonly diagnosed on random systematic biopsies prompted by elevated serum PSA levels. Multi-parametric MRI (MP-MRI) of the prostate has emerged as an anatomic and functional imaging modality, which offers accurate detection, localization and staging of prostate cancer. Recently, MP-MRI has gained an increasing role in guiding biopsies to sites of abnormality and in monitoring patients on active surveillance. Here, we discuss the historical development, current role, and potential future directions of MP-MRI in the diagnosis of prostate cancer.

Multiparametric magnetic resonance imaging of the prostate aids detect lesion progression

Multiparametric magnetic resonance imaging (MRI) provides an accurate anatomical assessment of the tumor and its local staging. Herein, we report a case of intermediate-risk prostatic adenocarcinoma, initially followed on active surveillance, which upgraded from Gleason 7 (3 + 4) to Gleason 8 (4 + 4) on transrectal ultrasound/MRI fusion biopsy after progression of MR spectroscopic findings and review of the role of multiparametric MRI in the follow-up of patients with prostate cancer undergoing active surveillance.

Optimization of prostate biopsy: the role of magnetic resonance imaging targeted biopsy in detection, localization and risk assessment

PURPOSE

Optimization of prostate biopsy requires addressing the shortcomings of standard systematic transrectal ultrasound guided biopsy, including false-negative rates, incorrect risk stratification, detection of clinically insignificant disease and the need for repeat biopsy. Magnetic resonance imaging is an evolving noninvasive imaging modality that increases the accurate localization of prostate cancer at the time of biopsy, and thereby enhances clinical risk assessment and improves the ability to appropriately counsel patients regarding therapy. In this review we 1) summarize the various sequences that comprise a prostate multiparametric magnetic resonance imaging examination along with its performance characteristics in cancer detection, localization and reporting standards; 2) evaluate potential applications of magnetic resonance imaging targeting in prostate biopsy among men with no previous biopsy, a negative previous biopsy and those with low stage cancer; and 3) describe the techniques of magnetic resonance imaging targeted biopsy and comparative study outcomes.

MATERIALS AND METHODS

A bibliographic search covering the period up to October 2013 was conducted using MEDLINE®/PubMed®. Articles were reviewed and categorized based on which of the 3 objectives of this review was addressed. Data were extracted, analyzed and summarized.

RESULTS

Multiparametric magnetic resonance imaging consists of anatomical T2-weighted imaging coupled with at least 2 functional imaging techniques. It has demonstrated improved prostate cancer detection sensitivity up to 80% in the peripheral zone and 81% in the transition zone. A prostate cancer magnetic resonance imaging suspicion score has been developed, and is depicted using the Likert or PI-RADS (Prostate Imaging Reporting and Data System) scale for better standardization of magnetic resonance imaging interpretation and reporting. Among men with no previous biopsy, magnetic resonance imaging increases the frequency of significant cancer detection to 50% in low risk and 71% in high risk patients. In low risk men the negative predictive value of a combination of negative magnetic resonance imaging with prostate volume parameters is nearly 98%, suggesting a potential role in avoiding biopsy and reducing over detection/overtreatment. Among men with a previous negative biopsy 72% to 87% of cancers detected by magnetic resonance imaging guidance are clinically significant. Among men with a known low risk cancer, repeat biopsy using magnetic resonance targeting demonstrates a high likelihood of confirming low risk disease in low suspicion score lesions and of upgrading in high suspicion score lesions. Techniques of magnetic resonance imaging targeted biopsy include visual estimation transrectal ultrasound guided biopsy; software co-registered magnetic resonance imaging-ultrasound, transrectal ultrasound guided biopsy; and in-bore magnetic resonance imaging guided biopsy. Although the improvement in accuracy and efficiency of visual estimation biopsy compared to systematic appears limited, co-registered magnetic resonance imaging-ultrasound biopsy as well as in-bore magnetic resonance imaging guided biopsy appear to increase cancer detection rates in conjunction with increasing suspicion score.

CONCLUSIONS

Use of magnetic resonance imaging for targeting prostate biopsies has the potential to reduce the sampling error associated with conventional biopsy by providing better disease localization and sampling. More accurate risk stratification through improved cancer sampling may impact therapeutic decision making. Optimal clinical application of magnetic resonance imaging targeted biopsy remains under investigation.

Multiparametric MRI in the PSA screening era

Prostate cancer remains significant public health concern amid growing controversies regarding prostate specific antigen (PSA) based screening. The utility of PSA has been brought into question, and alternative measures are investigated to remedy the overdetection of indolent disease and safeguard patients from the potential harms resulting from an elevated PSA. Multiparametric MRI of the prostate has shown promise in identifying patients at risk for clinically significant disease but its role within the current diagnostic and treatment paradigm remains in question. The current review focuses on recent applications of MRI in this pathway.

Identification of threshold prostate specific antigen levels to optimize the detection of clinically significant prostate cancer by magnetic resonance imaging/ultrasound fusion guided biopsy

PURPOSE

Prostate specific antigen sensitivity increases with lower threshold values but with a corresponding decrease in specificity. Magnetic resonance imaging/ultrasound targeted biopsy detects prostate cancer more efficiently and of higher grade than standard 12-core transrectal ultrasound biopsy but the optimal population for its use is not well defined. We evaluated the performance of magnetic resonance imaging/ultrasound targeted biopsy vs 12-core biopsy across a prostate specific antigen continuum.

MATERIALS AND METHODS

We reviewed the records of all patients enrolled in a prospective trial who underwent 12-core transrectal ultrasound and magnetic resonance imaging/ultrasound targeted biopsies from August 2007 through February 2014. Patients were stratified by each of 4 prostate specific antigen cutoffs. The greatest Gleason score using either biopsy method was compared in and across groups as well as across the population prostate specific antigen range. Clinically significant prostate cancer was defined as Gleason 7 (4 + 3) or greater. Univariate and multivariate analyses were performed.

RESULTS

A total of 1,003 targeted and 12-core transrectal ultrasound biopsies were performed, of which 564 diagnosed prostate cancer for a 56.2% detection rate. Targeted biopsy led to significantly more upgrading to clinically significant disease compared to 12-core biopsy. This trend increased more with increasing prostate specific antigen, specifically in patients with prostate specific antigen 4 to 10 and greater than 10 ng/ml. Prostate specific antigen 5.2 ng/ml or greater captured 90% of upgrading by targeted biopsy, corresponding to 64% of patients who underwent multiparametric magnetic resonance imaging and subsequent fusion biopsy. Conversely a greater proportion of clinically insignificant disease was detected by 12-core vs targeted biopsy overall. These differences persisted when controlling for potential confounders on multivariate analysis.

CONCLUSIONS

Prostate cancer upgrading with targeted biopsy increases with an increasing prostate specific antigen cutoff. Above a prostate specific antigen threshold of 5.2 ng/ml most upgrading to clinically significant disease was achieved by targeted biopsy. In our population this corresponded to potentially sparing biopsy in 36% of patients who underwent multiparametric magnetic resonance imaging. Below this value 12-core biopsy detected more clinically insignificant cancer. Thus, the diagnostic usefulness of targeted biopsy is optimized in patients with prostate specific antigen 5.2 ng/ml or greater.

Multiparametric 3T MRI for the prediction of pathological downgrading after radical prostatectomy in patients with biopsy-proven Gleason score 3 + 4 prostate cancer

OBJECTIVES

The aim of this study was to assess the diagnostic performance of pre-treatment 3-Tesla (3T) multiparametric magnetic resonance imaging (mpMRI) for predicting Gleason score (GS) downgrading after radical prostatectomy (RP) in patients with GS 3 + 4 prostate cancer (PCa) on biopsy.

METHODS

We retrospectively reviewed 304 patients with biopsy-proven GS 3 + 4 PCa who underwent mpMRI before RP. On T2-weighted imaging and three mpMRI combinations (T2-weighted imaging + diffusion-weighted imaging [DWI], T2-weighted imaging + dynamic contrast-enhanced-MRI [DCE-MRI], and T2-weighted imaging + DWI + DCE-MRI), two radiologists (R1/R2) scored the presence of a dominant tumour using a 5-point Likert scale (1 = definitely absent to 5 = definitely present). Diagnostic performance in identifying downgrading was evaluated via areas under the curves (AUCs). Predictive accuracies of multivariate models were calculated.

RESULTS

In predicting downgrading, T2-weighted imaging + DWI (AUC = 0.89/0.85 for R1/R2) performed significantly better than T2-weighted imaging alone (AUC = 0.72/0.73; p < 0.001/p = 0.02 for R1/R2), while T2-weighted imaging + DWI + DCE-MRI (AUC = 0.89/0.84 for R1/R2) performed no better than T2-weighted imaging + DWI (p = 0.48/p > 0.99 for R1/R2). On multivariate analysis, the clinical + mpMRI model incorporating T2-weighted imaging + DWI (AUC = 0.92/0.88 for R1/R2) predicted downgrading significantly better than the clinical model (AUC = 0.73; p < 0.001 for R1/R2).

CONCLUSION

mpMRI improves the ability to identify a subgroup of patients with Gleason 3 + 4 PCa on biopsy who are candidates for active surveillance. DCE-MRI (compared to T2 + DWI) offered no additional benefit to the prediction of downgrading.

KEY POINTS

Diagnostic performance of T2-weighted-imaging + DWI was better than T2-weighted-imaging alone. Diagnostic performance of T2-weighted-imaging + DWI was similar to T2-weighted-imaging + DWI + DCE-MRI. Combining clinical and T2-weighted-imaging + DWI features best predicted GS downgrading. mpMRI might prevent overtreatment by increasing eligibility for PCa active surveillance.

A prospective comparison of MRI-US fused targeted biopsy versus systematic ultrasound-guided biopsy for detecting clinically significant prostate cancer in patients on active surveillance

BACKGROUND

In active surveillance (AS) patients: (i) To compare the ability of a multiparametric MRI (mpMRI)-ultrasound biopsy system to detect clinically significant (CS) prostate cancer with systematic 12-core biopsy (R-TRUSBx), and (ii) To assess the predictive value of mpMRI with biopsy as the reference standard.

METHODS

Seventy-two men on AS prospectively underwent 3T mpMRI . MRI-ultrasound fusion biopsy (UroNavBx) and R-TRUSBx was performed. CS cancer was defined using two thresholds: 1) GS ≥ 7 (CS7) and 2) GS = 6 with >50% involvement (GS6). CS cancer detection rates and predictive values were determined.

RESULTS

CS7 cancers were found in 19/72 (26%), 7 (37%) identified by UroNavBx alone, 2 (11%) by R-TRUSBx alone (P = 0.182). UroNav targeted biopsy was 6.3× more likely to yield a core positive for CS7 cancer compared with R-TRUSBx (25% of 141 versus 4% of 874, P < 0.001). Upgrading of GS occurred in 15/72 patients (21%), 13 (87%) detected by UroNavBx and 10 (67%) by R-TRUSBx. The NPV of mpMRI for CS7 cancer was 100%. MRI suspicion level significantly predicted CS cancer on multivariate analysis (OR 3.6, P < 0.001).

CONCLUSION

UroNavBx detected CS cancer with far fewer cores compared with R-TRUSBx, and mpMRI had a perfect negative predictive value in this population.