Transrectal ultrasound-guided biopsy of prostate voxels identified as suspicious of malignancy on three-dimensional (1)H MR spectroscopic imaging in patients with abnormal digital rectal examination or raised prostate specific antigen level of 4-10 ng/ml

Patients With "Gray Zone" PSA Levels: Application of Prostate MRI and MRS in the Diagnosis of Prostate Cancer

Improving the detection rates of prostate cancer (PCa) and avoiding unnecessary prostate biopsies in men with prostate-specific antigen (PSA) levels within the gray zone require urgent attention. In this context, rapid advances in MR technology in recent years may offer a promising possibility. A systematic review to evaluate the applications of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in detecting PCa and clinically significant PCa (csPCa) in men with PSA levels within the gray zone. The study type is defined as systematic review. In July 2022, out of 229 studies identified by the database search and from other sources, 23 articles related to the selected topic of interest were included in this review. No field strength or sequence restrictions. The data including the study population, study characteristics, as well as basic MRI characteristics, from the final studies included in this review, were extracted independently by two reviewers. The major results of the original study were summarized and no additional statistical analysis was performed. Among the 23 studies included in this review, 17 focused on the applications of MRS and MRI for the prebiopsy diagnosis of PCa. Nine of these 17 articles used Prostate Imaging Reporting and Data System (PI-RADS) score to interpret MRI results, thereby confirming the practicality of the PI-RADS score in predicting PCa and csPCa. The remaining six articles evaluated the applications of MRI and MRS in guiding prostate biopsy. Although there was a variation in the biopsy modalities used in these studies, both MRI- and MRS-guided prostate biopsies were observed to improve the detection rates of PCa and csPCa in patients with PSA levels within the gray zone. MRS and MRI showed good performance in the detection of PCa and csPCa before biopsy. In addition, MRS- or MRI-guided prostate-targeted biopsies were able to improve the detection rates of PCa and csPCa. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 2.

The Performance of FDA-Approved PET Imaging Agents in the Detection of Prostate Cancer

Positron emission tomography (PET) incorporated with X-ray computed tomography (PET/CT) or magnetic resonance imaging (PET/MRI) is increasingly being used as a diagnostic tool for prostate cancer (PCa). In this review, we describe and evaluate the clinical performance of some Food and Drug Administration (FDA)-approved agents used for visualizing PCa: [¹⁸F]FDG, [¹¹C]choline, [¹⁸F]FACBC, [⁶⁸Ga]Ga-PSMA-11, [¹⁸F]DCFPyL, and [¹⁸F]-NaF. We carried out a comprehensive literature search based on articles published from 1 January 2010 to 1 March 2022. We selected English language articles associated with the discovery, preclinical study, clinical study, and diagnostic performance of the imaging agents for the evaluation. Prostate-specific membrane antigen (PSMA)-targeted imaging agents demonstrated superior diagnostic performance in both primary and recurrent PCa, compared with [¹¹C]choline and [¹⁸F]FACBC, both of which target dividing cells and are used especially in patients with low prostate-specific antigen (PSA) values. When compared to [¹⁸F]-NaF (which is suitable for the detection of bone metastases), PSMA-targeted agents were also capable of detecting lesions in the lymph nodes, soft tissues, and bone. However, a limitation of PSMA-targeted imaging was the heterogeneity of PSMA expression in PCa, and consequently, a combination of two PET tracers was proposed to overcome this obstacle. The preliminary studies indicated that the use of PSMA-targeted scanning is more cost efficient than conventional imaging modalities for high-risk PCa patients. Furthering the development of imaging agents that target PCa-associated receptors and molecules could improve PET-based diagnosis of PCa.

Emerging MR methods for improved diagnosis of prostate cancer by multiparametric MRI

Current challenges of using serum prostate-specific antigen (PSA) level-based screening, such as the increased false positive rate, inability to detect clinically significant prostate cancer (PCa) with random biopsy, multifocality in PCa, and the molecular heterogeneity of PCa, can be addressed by integrating advanced multiparametric MR imaging (mpMRI) approaches into the diagnostic workup of PCa. The standard method for diagnosing PCa is a transrectal ultrasonography (TRUS)-guided systematic prostate biopsy, but it suffers from sampling errors and frequently fails to detect clinically significant PCa. mpMRI not only increases the detection of clinically significant PCa, but it also helps to reduce unnecessary biopsies because of its high negative predictive value. Furthermore, non-Cartesian image acquisition and compressed sensing have resulted in faster MR acquisition with improved signal-to-noise ratio, which can be used in quantitative MRI methods such as dynamic contrast-enhanced (DCE)-MRI. With the growing emphasis on the role of pre-biopsy mpMRI in the evaluation of PCa, there is an increased demand for innovative MRI methods that can improve PCa grading, detect clinically significant PCa, and biopsy guidance. To meet these demands, in addition to routine T1-weighted, T2-weighted, DCE-MRI, diffusion MRI, and MR spectroscopy, several new MR methods such as restriction spectrum imaging, vascular, extracellular, and restricted diffusion for cytometry in tumors (VERDICT) method, hybrid multi-dimensional MRI, luminal water imaging, and MR fingerprinting have been developed for a better characterization of the disease. Further, with the increasing interest in combining MR data with clinical and genomic data, there is a growing interest in utilizing radiomics and radiogenomics approaches. These big data can also be utilized in the development of computer-aided diagnostic tools, including automatic segmentation and the detection of clinically significant PCa using machine learning methods.

Accuracy of multiparametric magnetic resonance imaging for diagnosing prostate Cancer: a systematic review and meta-analysis

Background

The application of multiparametric magnetic resonance imaging (mpMRI) for diagnosis of prostate cancer has been recommended by the European Association of Urology (EAU), National Comprehensive Cancer Network (NCCN), and European Society of Urogenital Radiology (ESUR) guidelines. The purpose of this study is to systematically review the literature on assessing the accuracy of mpMRI in patients with suspicion of prostate cancer.

Method

We searched Embase, Pubmed and Cochrane online databases from January 12,000 to October 272,018 to extract articles exploring the possibilities that the pre-biopsy mpMRI can enhance the diagnosis accuracy of prostate cancer. The numbers of true- and false-negative results and true- and false-positive ones were extracted to calculate the corresponding sensitivity and specificity of mpMRI. Study quality was assessed using QUADAS-2 tool. Random effects meta-analysis and a hierarchical summary receiver operating characteristic (HSROC) plot were performed for further study.

Results

After searching, we acquired 3741 articles for reference, of which 29 studies with 8503 participants were eligible for inclusion. MpMRI maintained impressive diagnostic value, the area under the HSROC curve was 0.87 (95%CI,0.84–0.90). The sensitivity and specificity for mpMRI were 0.87 [95%CI, 0.81–0.91] and 0.68 [95%CI,0.56–0.79] respectively. The positive likelihood ratio was 2.73 [95%CI 1.90–3.90]; negative likelihood ratio was 0.19 [95% CI 0.14,-0.27]. The risk of publication bias was negligible with P = 0.96.

Conclusion

Results of the meta-analysis suggest that mpMRI is a sensitive tool to diagnose prostate cancer. However, because of the high heterogeneity existing among the included studies, further studies are needed to apply the results of this meta-analysis in clinic.

Multiparametric (mp) MRI of prostate cancer

Prostate cancer (PCa) is one of the most prevalent cancers in men. A large number of men are detected with PCa; however, the clinical behavior ranges from low-grade indolent tumors that never develop into a clinically significant disease to aggressive, invasive tumors that may rapidly progress to metastatic disease. The challenges in clinical management of PCa are at levels of screening, diagnosis, treatment, and follow-up after treatment. Magnetic resonance imaging (MRI) methods have shown a potential role in detection, localization, staging, assessment of aggressiveness, targeting biopsies, etc. in PCa patients. Multiparametric MRI (mpMRI) is emerging as a better option compared to the individual imaging methods used in the evaluation of PCa. There are attempts to improve the reproducibility and reliability of mpMRI by using an objective scoring system proposed in the prostate imaging reporting and data system (PIRADS) for standardized reporting. Prebiopsy mpMRI may be used to detect PCa in men with elevated prostate-specific antigen or abnormal digital rectal examination and to enable targeted biopsies. mpMRI can also be used to decide on clinical management of patients, for example active surveillance, and may help in detecting only the pathology that requires detection. It can potentially not only guide patient selection for initial and repeat biopsy but also reduce false-negative biopsies. This review presents a description of the MR methods most commonly applied for investigations of prostate. The anatomical, functional and metabolic parameters obtained from these MR methods are discussed with regard to their physical basis and their contribution to mpMRI investigations of PCa.

Prebiopsy multiparametric MRI-based risk score for predicting prostate cancer in biopsy-naive men with prostate-specific antigen between 4-10 ng/mL

BACKGROUND

Risk calculators have traditionally utilized serum prostate-specific antigen (PSA) values in addition to clinical variables to predict the likelihood of prostate cancer (PCa).

PURPOSE

To develop a prebiopsy multiparametric MRI (mpMRI)-based risk score (RS) and a statistical equation for predicting the risk of PCa in biopsy-naive men with serum PSA between 4-10 ng/mL that may help reduce unnecessary biopsies.

STUDY TYPE

Prospective cross-sectional study.

SUBJECTS

In all, 137 consecutive men with PSA between 4-10 ng/mL underwent prebiopsy mpMRI (diffusion-weighted [DW]-MRI and MR spectroscopic imaging [MRSI]) during 2009-2015 were recruited for this study.

FIELD STRENGTH/SEQUENCE

1.5T (Avanto, Siemens Health Care, Erlangen, Germany); T₁ -weighted, T₂ -weighted, DW-MRI, and MRSI sequences were used.

ASSESSMENT

All eligible patients underwent mpMRI-directed, cognitive-fusion transrectal ultrasound (TRUS)-guided biopsies.

STATISTICAL TESTS

An equation model and an RS were developed using receiver operating characteristic (ROC) curve analysis and a multivariable logistic regression approach. A 10-fold crossvalidation and simulation analyses were performed to assess diagnostic performance of various combinations of mpMRI parameters.

RESULTS

Of 137 patients, 32 were diagnosed with PCa on biopsy. Multivariable analysis, adjusted with positive pathology, showed apparent diffusion coefficient (ADC), metabolite ratio, and PSA as significant predictors of PCa (P < 0.05). A statistical equation was derived using these predictors. A simple 6-point mpMRI-based RS was derived for calculating the risk of PCa and it showed that it is highly predictive for PCa (odds ratio = 3.74, 95% confidence interval [CI]: 2.24-6.27, area under the curve [AUC] = 0.87). Both models (equation and RS) yielded high predictive performance (AUC ≥0.85) on validation analysis.

DATA CONCLUSION

A statistical equation and a simple 6-point mpMRI-based RS can be used as a point-of-care tool to potentially help limit the number of negative biopsies in men with PSA between 4 and 10 ng/mL.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1227-1236.

What Is the Negative Predictive Value of Multiparametric Magnetic Resonance Imaging in Excluding Prostate Cancer at Biopsy? A Systematic Review and Meta-analysis from the European Association of Urology Prostate Cancer Guidelines Panel

CONTEXT

It remains unclear whether patients with a suspicion of prostate cancer (PCa) and negative multiparametric magnetic resonance imaging (mpMRI) can safely obviate prostate biopsy.

OBJECTIVE

To systematically review the literature assessing the negative predictive value (NPV) of mpMRI in patients with a suspicion of PCa.

EVIDENCE ACQUISITION

The Embase, Medline, and Cochrane databases were searched up to February 2016. Studies reporting prebiopsy mpMRI results using transrectal or transperineal biopsy as a reference standard were included. We further selected for meta-analysis studies with at least 10-core biopsies as the reference standard, mpMRI comprising at least T2-weighted and diffusion-weighted imaging, positive mpMRI defined as a Prostate Imaging Reporting Data System/Likert score of ≥3/5 or ≥4/5, and results reported at patient level for the detection of overall PCa or clinically significant PCa (csPCa) defined as Gleason ≥7 cancer.

EVIDENCE SYNTHESIS

A total of 48 studies (9613 patients) were eligible for inclusion. At patient level, the median prevalence was 50.4% (interquartile range [IQR], 36.4-57.7%) for overall cancer and 32.9% (IQR, 28.1-37.2%) for csPCa. The median mpMRI NPV was 82.4% (IQR, 69.0-92.4%) for overall cancer and 88.1% (IQR, 85.7-92.3) for csPCa. NPV significantly decreased when cancer prevalence increased, for overall cancer (r=-0.64, p<0.0001) and csPCa (r=-0.75, p=0.032). Eight studies fulfilled the inclusion criteria for meta-analysis. Seven reported results for overall PCa. When the overall PCa prevalence increased from 30% to 60%, the combined NPV estimates decreased from 88% (95% confidence interval [95% CI], 77-99%) to 67% (95% CI, 56-79%) for a cut-off score of 3/5. Only one study selected for meta-analysis reported results for Gleason ≥7 cancers, with a positive biopsy rate of 29.3%. The corresponding NPV for a cut-off score of ≥3/5 was 87.9%.

CONCLUSIONS

The NPV of mpMRI varied greatly depending on study design, cancer prevalence, and definitions of positive mpMRI and csPCa. As cancer prevalence was highly variable among series, risk stratification of patients should be the initial step before considering prebiopsy mpMRI and defining those in whom biopsy may be omitted when the mpMRI is negative.

PATIENT SUMMARY

This systematic review examined if multiparametric magnetic resonance imaging (MRI) scan can be used to reliably predict the absence of prostate cancer in patients suspected of having prostate cancer, thereby avoiding a prostate biopsy. The results suggest that whilst it is a promising tool, it is not accurate enough to replace prostate biopsy in such patients, mainly because its accuracy is variable and influenced by the prostate cancer risk. However, its performance can be enhanced if there were more accurate ways of determining the risk of having prostate cancer. When such tools are available, it should be possible to use an MRI scan to avoid biopsy in patients at a low risk of prostate cancer.

Multiparametric MR can identify high grade prostatic intraepithelial neoplasia (HGPIN) lesions and predict future detection of prostate cancer in men with a negative initial prostate biopsy

PURPOSE

This study aims to determine the pre-biopsy diffusion-weighted imaging (DWI) and magnetic resonance spectroscopic imaging (MRSI) characteristics of patients with high-grade prostatic intraepithelial neoplasia (HGPIN) and perform follow-up studies in these patients to assess the clinical implications.

MATERIALS AND METHODS

One hundred sixteen men with prostate specific antigen between 4 and 10ng/ml underwent pre-biopsy MR examinations. Nine of them had HGPIN lesions without concomitant prostate cancer (PCa) on biopsy. Apparent diffusion coefficient (ADC) and metabolite ratio [Citrate/(Choline+Creatine)] were calculated and these 9 patients were followed to determine the clinical outcomes.

RESULTS

Mean ADC for HGPIN foci was 1.01±0.16×10(-3)mm(2)/s while for the normal peripheral zone it was 1.69±0.25×10(-3)mm(2)/s (p<0.005). Mean metabolite ratio for voxels in the HGPIN region of initial biopsy was 0.24±0.16 while for the normal peripheral zone the value was 2.66±1.57 (p<0.005). Four of 5 patients who were available for follow-up were detected to have prostate cancer on repeat biopsy. No significant change in metabolite ratio and PSA was observed while ADC showed further reduction on follow-up.

CONCLUSION

HGPIN foci have ADC and metabolite ratio values similar to adenocarcinoma prostate, indicating that such patients have a high likelihood of developing cancer. DWI may help identify such men who may be candidates for close follow-up.

Imaging and intervention in prostate cancer: Current perspectives and future trends

Prostate cancer is the commonest malignancy in men that causes significant morbidity and mortality worldwide. Screening by digital rectal examination (DRE) and serum prostate-specific antigen (PSA) is used despite its limitations. Gray-scale transrectal ultrasound (TRUS), used to guide multiple random prostatic biopsies, misses up to 20% cancers and frequently underestimates the grade of malignancy. Increasing the number of biopsy cores marginally increases the yield. Evolving techniques of real-time ultrasound elastography (RTE) and contrast-enhanced ultrasound (CEUS) are being investigated to better detect and improve the yield by allowing “targeted” biopsies. Last decade has witnessed rapid developments in magnetic resonance imaging (MRI) for improved management of prostate cancer. In addition to the anatomical information, it is capable of providing functional information through diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), and dynamic contrast-enhanced (DCE) MRI. Multi-parametric MRI has the potential to exclude a significant cancer in majority of cases. Inclusion of MRI before prostatic biopsy can reduce the invasiveness of the procedure by limiting the number of cores needed to make a diagnosis and support watchful waiting in others. It is made possible by targeted biopsies as opposed to random. With the availability of minimally invasive therapeutic modalities like high-intensity focused ultrasound (HIFU) and interstitial laser therapy, detecting early cancer is even more relevant today. [18F]--fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸FDG PET/CT) has no role in the initial evaluation of prostate cancer. Choline PET has been recently found to be more useful. Fluoride-PET has a higher sensitivity and resolution than a conventional radionuclide bone scan in detecting skeletal metastases.

The value of magnetic resonance imaging in the detection of prostate cancer in patients with previous negative biopsies and elevated prostate-specific antigen levels: a meta-analysis

RATIONALE AND OBJECTIVES

To assess the diagnostic performance of magnetic resonance imaging (MRI) for targeting prostate cancer in patients with previous negative biopsies and elevated prostate-specific antigen (PSA) levels.

MATERIALS AND METHODS

Pubmed, Scopus, and Cochrane Library databases were searched to identify suitable studies published from January 2001 to October 2013. Polled estimation and subgroup analysis data were obtained using a random effect model. Summary receiver operating characteristic curves were used to summarize overall test performance.

RESULTS

Fourteen studies involving 698 patients met the included criteria. The mean prostate cancer detection rate was 37.5%. Twelve studies had a pooled sensitivity, specificity, and diagnostic odds ratio (DOR) of 88%, 69%, and 16.84 by patient analysis, respectively. In the subgroup analysis, magnetic resonance imaging spectroscopy (MRSI) provided higher pooled sensitivity (91%) and specificity (69%) compared with T2-weighted imaging (T2WI). MRSI combined with MRI had the highest pooled specificity (73%). By site analysis, the pooled sensitivity, specificity, and DOR in nine studies were 57%, 90%, and 14.34, respectively. In the subgroup analysis, MRSI combined with MRI showed higher pooled sensitivity (58%) and specificity (93%) compared with T2WI. Diffusion-weighted MRI (DWI) showed the highest pooled specificity: 95% but the lowest pooled sensitivity: 38%.

CONCLUSIONS

A limited number of studies suggest that the value of MRI to target prostate cancer in patients with previous negative biopsies and elevated PSA levels appears significant. MRI combined with MRSI is particularly accurate. Further studies are necessary to confirm the eventual role of DWI in this field.

Role of MRI in prostate cancer detection

The standard approach for the detection of prostate cancer--prostate-specific antigen (PSA) screening followed by transrectal ultrasonography (TRUS)-guided biopsy--has low sensitivity and provides limited information about the true extent and aggressiveness of the cancer. Improved methods are needed to assess the extent and aggressiveness of the cancer and to identify patients who will benefit from therapy. In recent years, there has been tremendous development of acquisition and processing tools for physiological and metabolic MRI techniques which play a potential role in the detection, localization and characterization of prostate cancer, such as dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted MRI (DW-MRI) and/or proton MR spectroscopic imaging ((1)H MRSI). The standard protocol for prostate MRI without the use of a contrast agent involves multi-planar T1 -weighted MRI, T2 -weighted MRI and DW-MRI. This review discusses the potential role of MRI in the detection of prostate cancer, specifically describing the status of MRI as a tool for guiding targeted prostate biopsies and for detecting cancer in the untreated and treated gland. In addition, future areas of MRI research are briefly discussed. Groups conducting clinical trials should consider the recommendations put forward by the European Consensus Meeting, which state that the minimum requirements for prostate MRI are T1 -weighted MRI, T2 -weighted MRI, DCE-MRI (which involves the use of a contrast agent) and DW-MRI with a pelvic phased-array coil and propose the use of transperineal template mapping biopsies as the optimal reference standard.

MRI-targeted prostate biopsy: a review of technique and results

Multiparametric magnetic resonance imaging (mpMRI) is of interest for the diagnosis of clinically significant prostate cancer and mpMRI-targeted biopsies are being used increasingly in clinical practice. Target acquisition is performed using a range of magnet strengths and varying combinations of anatomical and functional sequences. Target identification at the time of biopsy can be carried out in the MRI scanner (in-bore biopsy) or, more commonly, the MRI-target is biopsied under ultrasonographic guidance. Many groups use cognitive or visual registration, whereby the biopsy target is identified on MRI and ultrasonography is subsequently used to direct the needle to the same location. Other groups use registration software to show prebiopsy MRI data on real-time ultrasonography. The reporting of histological results in MRI-targeted biopsy studies varies greatly. The most useful reports compare the detection of clinically significant disease in standard cores versus mpMRI-targeted cores in the same cohort of men, as recommended by the STAndards of Reporting for MRI-Targeted biopsy studies (START) consensus panel. Further evidence is needed before an mpMRI-targeted strategy can be recommended as the standard intervention for men at risk of prostate cancer.

Magnetic resonance spectroscopy imaging-directed transrectal ultrasound biopsy increases prostate cancer detection in men with prostate-specific antigen between 4-10 ng/mL and normal digital rectal examination

OBJECTIVES

To evaluate the ability of magnetic resonance spectroscopic imaging to improve prostate cancer detection rate.

METHODS

A retrospective analysis was carried out of 278 men with prostate-specific antigen in the range of 4-10 ng/mL and normal digital rectal examination who underwent transrectal ultrasound-guided prostate biopsy. Outcomes were compared between men who had a standard biopsy versus those who also underwent a prebiopsy magnetic resonance spectroscopic imaging. Men with an abnormal voxel on magnetic resonance spectroscopic imaging had standard transrectal ultrasound biopsies plus biopsies directed to the abnormal voxels.

RESULTS

The study group (n = 140) and control group (n = 138) were similar in baseline parameters, such as mean age, prostate size and mean prostate-specific antigen. The overall cancer detection in the magnetic resonance spectroscopic imaging positive group (24.4%) was more than double that of the control group (10.1%). On comparing the magnetic resonance spectroscopic imaging results with the transrectal ultrasound biopsy findings, magnetic resonance spectroscopic imaging had 95.6% sensitivity, 41.9% specificity, a positive predictive value of 24.4%, a negative predictive value of 98% and an accuracy of 51.4%.

CONCLUSIONS

Magnetic resonance spectroscopic imaging-directed transrectal ultrasound biopsy increases the cancer detection rate compared with standard transrectal ultrasound biopsy in patients with normal digital rectal examination and elevated prostate-specific antigen in the range of 4-10 ng/mL.

Diagnosis of relevant prostate cancer using supplementary cores from magnetic resonance imaging-prompted areas following multiple failed biopsies

OBJECTIVES

To establish the value of MRI in targeting re-biopsy for undiagnosed prostate cancer despite multiple negative biopsies and determine clinical relevance of detected tumors.

MATERIALS AND METHODS

Thirty-eight patients who underwent MRI after 2 or more negative biopsies due to continued clinical suspicion and later underwent TRUS-guided biopsy supplemented by biopsy of suspicious areas depicted by MRI were identified. Diagnostic performance of endorectal 3T MRI in diagnosing missed cancer foci was assessed using biopsy results as the standard of reference. Ratio of positive biopsies using systematic versus MRI-prompted approaches was compared. Gleason scores of detected cancers were used as surrogate for clinical relevance.

RESULTS

Thirty-four percent of patients who underwent MRI before re-biopsy had prostate cancer on subsequent biopsy. The positive biopsy yield with systematic sampling was 23% versus 92% with MRI-prompted biopsies(p<0.0001). Seventy-seven percent of tumors were detected exclusively in the MRI-prompted zones. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of MRI to provide a positive biopsy were 92%, 60%, 55%, 94% and 71%, respectively. The anterior gland and apical regions contained most tumors; 75% of cancers detected by MRI-prompted biopsy had Gleason score≥7.

CONCLUSIONS

Clinically relevant tumors missed by multiple TRUS-guided biopsies can be detected by a MRI-prompted approach.

Imaging-guided prostate biopsy: conventional and emerging techniques

Transrectal ultrasonography (US)-guided biopsy is the standard approach for histopathologic diagnosis of prostate cancer. However, this technique has multiple limitations owing to the operator's inability in most cases to directly visualize and target prostate lesions. Magnetic resonance (MR) imaging of the prostate overcomes many of these limitations by directly depicting areas of abnormality and allowing targeted biopsies. Accuracy in the detection of prostate cancer is improved by the combined use of standard T2-weighted MR imaging and advanced MR imaging techniques such as diffusion-weighted imaging, dynamic contrast-enhanced imaging, and MR spectroscopy. Suspicious-appearing regions of the prostate seen on MR images can be targeted at real-time transrectal US-guided biopsy to improve the diagnostic yield. MR imaging also can be performed for real-time guidance of transrectal prostate biopsy. Studies among patients who underwent at least one transrectal US-guided biopsy with a negative result before undergoing an MR imaging-guided biopsy showed improved detection rates with MR imaging-guided biopsy in comparison with the detection rates achieved with a repeat transrectal US-guided biopsy; however, MR imaging-guided biopsy is a more time-consuming procedure. A technique known as fused MR imaging- and transrectal US-guided biopsy, which relies on the coregistration of previously acquired MR images with real-time transrectal US images acquired during the procedure, shows promise but is limited by deformation of the prostate; this limitation is the subject of ongoing investigation. Another technique that is currently under investigation, MR imaging-guided prostate biopsy with robotic assistance, may one day help improve the accuracy of biopsy needle placement.

A positive magnetic resonance spectroscopic imaging with negative initial biopsy may predict future detection of prostate cancer

Current diagnostic modalities for early prostate cancer (PCa) lack sufficient sensitivity and specificity. Magnetic resonance spectroscopic imaging (MRSI) detects biochemical changes in tissues that may predate histological changes that can be diagnosed on a biopsy. Men with MRSI suggestive of malignancy but negative biopsy may thus be harboring cancer that manifests at a later date. We report the first case in our cohort of men with positive MRSI but negative initial biopsy who, 6 years after the initial MRSI, were detected to have PCa despite a “normal” prostate specific antigen (<4.0 ng/ml).

Defining prostate cancer risk before prostate biopsy

Prostate cancer is the most commonly diagnosed cancer in men. At present, patients are selected for prostate biopsy on the basis of age, serum prostate specific antigen (PSA), and prostatic digital rectal examination (DRE) findings. However, due to limitations in the use of PSA and DRE, many patients undergo unnecessary prostate biopsy. A further problem arises as many patients are diagnosed and treated for indolent disease. This review of the literature highlights the strengths and weaknesses of existing methods of prebiopsy risk stratification and evaluates promising serum, urine, and radiologic prostate cancer biomarkers, which may improve risk stratification for prostate biopsy in the future.

Image-guided prostate biopsy using magnetic resonance imaging-derived targets: a systematic review

CONTEXT

Technical improvements in prostate magnetic resonance imaging (MRI) have resulted in the use of MRI to target prostate biopsies.

OBJECTIVE

To systematically review the literature to compare the accuracy of MRI-targeted biopsy with standard transrectal biopsy in the detection of clinically significant prostate cancer.

EVIDENCE ACQUISITION

The PubMed, Embase, and Cochrane databases were searched from inception until December 3, 2011, using the search criteria 'prostate OR prostate cancer' AND 'magnetic resonance imaging OR MRI' AND 'biopsy OR target'. Four reviewers independently assessed 4222 records; 222 records required full review. Fifty unique records (corresponding to 16 discrete patient populations) directly compared an MRI-targeted with a standard transrectal approach.

EVIDENCE SYNTHESIS

Evidence synthesis was used to address specific questions. Where MRI was applied to all biopsy-naive men, 62% (374 of 599) had MRI abnormalities. When subjected to a targeted biopsy, 66% (248 of 374) had prostate cancer detected. Both targeted and standard biopsy detected clinically significant cancer in 43% (236 or 237 of 555, respectively). Missed clinically significant cancers occurred in 13 men using targeted biopsy and 12 using a standard approach. Targeted biopsy was more efficient. A third fewer men were biopsied overall. Those who had biopsy required a mean of 3.8 targeted cores compared with 12 standard cores. A targeted approach avoided the diagnosis of clinically insignificant cancer in 53 of 555 (10%) of the presenting population.

CONCLUSIONS

MRI-guided biopsy detects clinically significant prostate cancer in an equivalent number of men versus standard biopsy. This is achieved using fewer biopsies in fewer men, with a reduction in the diagnosis of clinically insignificant cancer. Variability in study methodology limits the strength of recommendation that can be made. There is a need for a robust multicentre trial of targeted biopsies.

Prebiopsy magnetic resonance spectroscopy and imaging in the diagnosis of prostate cancer

INTRODUCTION

Existing screening investigations for the diagnosis of early prostate cancer lack specificity, resulting in a high negative biopsy rate. There is increasing interest in the use of various magnetic resonance methods for improving the yield of transrectal ultrasound-guided biopsies of the prostate in men suspected to have prostate cancer. We review the existing status of such investigations.

METHODS

A literature search was carried out using the Pubmed database to identify articles related to magnetic resonance methods for diagnosing prostate cancer. References from these articles were also extracted and reviewed.

RESULTS

Recent studies have focused on prebiopsy magnetic resonance investigations using conventional magnetic resonance imaging, dynamic contrast enhanced magnetic resonance imaging, diffusion weighted magnetic resonance imaging, magnetization transfer imaging and magnetic resonance spectroscopy of the prostate. This marks a shift from the earlier strategy of carrying out postbiopsy magnetic resonance investigations. Prebiopsy magnetic resonance investigations has been useful in identifying patients who are more likely to have a biopsy positive for malignancy.

CONCLUSIONS

Prebiopsy magnetic resonance investigations has a potential role in increasing specificity of screening for early prostate cancer. It has a role in the targeting of biopsy sites, avoiding unnecessary biopsies and predicting the outcome of biopsies.

Prostate cancer: multiparametric MR imaging for detection, localization, and staging

This review presents the current state of the art regarding multiparametric magnetic resonance (MR) imaging of prostate cancer. Technical requirements and clinical indications for the use of multiparametric MR imaging in detection, localization, characterization, staging, biopsy guidance, and active surveillance of prostate cancer are discussed. Although reported accuracies of the separate and combined multiparametric MR imaging techniques vary for diverse clinical prostate cancer indications, multiparametric MR imaging of the prostate has shown promising results and may be of additional value in prostate cancer localization and local staging. Consensus on which technical approaches (field strengths, sequences, use of an endorectal coil) and combination of multiparametric MR imaging techniques should be used for specific clinical indications remains a challenge. Because guidelines are currently lacking, suggestions for a general minimal protocol for multiparametric MR imaging of the prostate based on the literature and the authors' experience are presented. Computer programs that allow evaluation of the various components of a multiparametric MR imaging examination in one view should be developed. In this way, an integrated interpretation of anatomic and functional MR imaging techniques in a multiparametric MR imaging examination is possible. Education and experience of specialist radiologists are essential for correct interpretation of multiparametric prostate MR imaging findings. Supportive techniques, such as computer-aided diagnosis are needed to obtain a fast, cost-effective, easy, and more reproducible prostate cancer diagnosis out of more and more complex multiparametric MR imaging data.

Prostate cancer detection in patients with total serum prostate-specific antigen levels of 4-10 ng/mL: diagnostic efficacy of diffusion-weighted imaging, dynamic contrast-enhanced MRI, and T2-weighted imaging

OBJECTIVE

The purpose of this study is to evaluate the utility of T2-weighted imaging, dynamic contrast-enhanced MRI (DCE-MRI), and diffusion-weighted imaging (DWI) for detecting prostate cancer in patients with total serum prostate-specific antigen (PSA) levels of 4-10 ng/mL, which is referred to as the "gray zone."

MATERIALS AND METHODS

Fifty patients with gray-zone PSA levels underwent MRI before biopsy. According to the sites of biopsy, the prostate was divided into eight regions on MRI scans. These regions were evaluated individually for the following features: detectability of prostate cancer on per-region and per-patient bases, and relationship between tumor size and positive or negative MRI findings for tumor detection.

RESULTS

On a per-region basis, the sensitivity and specificity of tumor detection were 36% and 97% for T2-weighted imaging, 43% and 95% for DCE-MRI, 38% and 96% for DWI, and 53% and 93% for the combined method of MRI, respectively. The sensitivity of combined MRI to detect tumor was significantly higher than those of the individual methods (p < 0.001 to p = 0.001). Tumor size was significantly larger in regions with positive MRI findings than in regions with negative MRI findings (p = 0.004). On a per-patient basis, sensitivity and specificity of combined MRI to detect prostate cancer were 83% and 80%, respectively.

CONCLUSION

Combined T2-weighted imaging, DWI, and DCE-MRI findings appear to be potentially useful for detecting and managing prostate cancer, even when performed for patients with gray-zone PSA levels.

A decade in prostate cancer: from NMR to metabolomics

Over the past 30 years, continuous progress in the application of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance spectroscopic imaging (MRSI) to the detection, diagnosis and characterization of human prostate cancer has turned what began as scientific curiosity into a useful clinical option. In vivo MRSI technology has been integrated into the daily care of prostate cancer patients, and innovations in ex vivo methods have helped to establish NMR-based prostate cancer metabolomics. Metabolomic and multimodality imaging could be the future of the prostate cancer clinic--particularly given the rationale that more accurate interrogation of a disease as complex as human prostate cancer is most likely to be achieved through paradigms involving multiple, instead of single and isolated, parameters. The research and clinical results achieved through in vivo MRSI and ex vivo NMR investigations during the first 11 years of the 21st century illustrate areas where these technologies can be best translated into clinical practice.

Accuracy of MRI/MRSI-based transrectal ultrasound biopsy in peripheral and transition zones of the prostate gland in patients with prior negative biopsy

The purpose of the study was to evaluate the accuracy of transrectal ultrasound biopsy (TRUS-biopsy) performed on regions with abnormal MRI and/or MRSI for both the transition (TZ) and the peripheral (PZ) zones in patients with suspected prostate cancer with prior negative biopsy, and to analyze the relationship between MRSI and histopathological findings. MRI and MRSI were performed in 54 patients (mean age: 63.9 years, mean PSA value: 11.4 ng/mL) and the ability of MRI/MRSI-directed TRUS biopsy was evaluated. A three-point score system was used for both techniques to distinguish healthy from malignant regions. Descriptive statistics and ROC analyses were performed to evaluate the accuracy and the best cut-off in the three-point score system. Twenty-two out of 54 patients presented cancer at MRI/MRSI-directed TRUS biopsy, nine presented cancer only in PZ, eight both in PZ and TZ, and five exclusively in TZ. On a patient basis the highest accuracy was obtained by assigning malignancy on a positive finding with MRSI and MRI even though it was not significantly greater than that obtained using MRI alone (area under the ROC curve, AUC: 0.723 vs 0.676). On a regional (n = 648) basis the best accuracy was also obtained by considering positive both MRSI and MRI for PZ (0.768) and TZ (0.822). MRSI was false positive in 11.9% of the regions. Twenty-eight percent of cores with prostatitis were false positive findings on MRSI, whereas only 2.7% of benign prostatic hyperplasia was false positive. In conclusion, the accuracy of MRI/MRSI-directed biopsies in localization of prostate cancer is good in patient (0.723) and region analyses (0.768). The combination of both MRI and MRSI results makes TRUS-biopsy more accurate, particularly in the TZ (0.822) for patients with prior negative biopsies. Histopathological analysis showed that the main limitation of MRSI is the percentage of false positive findings due to prostatitis.

Technique for a hybrid system of real-time transrectal ultrasound with preoperative magnetic resonance imaging in the guidance of targeted prostate biopsy

Diagnostic magnetic resonance imaging (MRI) for prostate has achieved increasingly higher levels of accuracy. Because real-time MR-guided targeted biopsy is still a complicated and expensive procedure, there is considerable interest in a technique of MR/transrectal ultrasound (TRUS) hybridized image-guided biopsy. However, because the 3-D shapes of the prostate at the time of image-acquisition at preoperative MRI are likely to be different from the intra-operative TRUS images, the precise registration of each 3-D volume data is critical. To reduce the potential errors in registration of TRUS with MRI, we introduce new procedural techniques in a rigid image fusion technique. First, preoperative MR images were obtained with a specifically-made plastic outer-frame, with exactly the same shape as the real TRUS probe, placed in the rectum, in order to simulate the deformation of the prostate caused by the absence or presence of a TRUS probe during the acquisition of MR or TRUS images. Second, instead of using a single plane of longitudinal image, we applied biplane TRUS images to be shown in parallel on a multiplanar display with corresponding reconstructed MRI, in order to register both horizontal and longitudinal images of the prostate simultaneously, thereby achieving improved 3-D anatomical matching.

Is it time to consider a role for MRI before prostate biopsy?

The use of MRI in prostate cancer management is controversial and current guidelines underplay its role. Technological advances over the past 5 years, however, demand a re-evaluation of this position. In this article, we propose an increased use of MRI, not only in those with a diagnosis of prostate cancer but also for men before a prostate biopsy. The use of MRI before a biopsy can serve as a triage test in men with raised serum prostate-specific antigen levels, in order to select those for biopsy with significant cancer that requires treatment. This strategy could avoid biopsy, and hence unnecessary treatment, in those with no disease or insignificant cancer. In addition, avoidance of postbiopsy artifact caused by hemorrhage will lead to better local staging accuracy, while determining more accurately the disease burden. This approach could improve risk stratification by selecting those who require adjuvant therapy or dose escalation. Furthermore, MRI evaluation of cancer burden could be important in active surveillance regimens to select those needing intervention.

Lesion localization in patients with a previous negative transrectal ultrasound biopsy and persistently elevated prostate specific antigen level using diffusion-weighted imaging at three Tesla before rebiopsy

OBJECTIVE

To assess the use of diffusion-weighted imaging (DWI) at 3 Tesla (T) for lesion localization in patients with a high risk of prostate cancer before a rebiopsy.

MATERIALS AND METHODS

A total of 43 patients (age range, 40-80 years; mean age, 62.6 years) who had previously undergone a transrectal ultrasound (TRUS)-guided biopsy that was negative and continued to have a persistent elevated prostate specific antigen level underwent DWI with b = 0 s/mm and b = 1000 s/mm before a rebiopsy. We located the area of the lowest apparent diffusion coefficient values and performed a target biopsy of that area, followed by a systematic biopsy under TRUS guidance. We evaluated the cancer detection rate, tumor location, and lesion visibility on T2-weighted imaging (T2WI) in patients with biopsy-proven cancers.

RESULTS

Prostate cancer was detected in 17 (39.5%) patients, and was more predominant in the transitional zone (76.4%, 13/17) than in the peripheral zone (23.6%, 4/17) (P < 0.05). Of the 17 cancers detected on DWI, 6 lesions were seen on T2WI.

CONCLUSION

DWI in addition to T2WI at 3 T has the potential to provide important information on lesion localization in patients that had both previous negative TRUS biopsy and persistently elevated prostate specific antigen levels before a repeated biopsy.

Potential of magnetic resonance spectroscopic imaging in predicting absence of prostate cancer in men with serum prostate-specific antigen between 4 and 10 ng/ml: a follow-up study

OBJECTIVES

Screening for prostate cancer using serum prostate-specific antigen (PSA) determination has a positive predictive value of only 30% to 42% for a PSA level between 4 and 10 ng/mL. Magnetic resonance spectroscopic imaging (MRSI), which identifies cancer on the basis of changes in cellular metabolite levels, might be able to identify patients with noncancerous PSA elevation and help avoid unnecessary biopsies. We tested this hypothesis by evaluating the incidence of prostate cancer in men with a PSA level of 4 to 10 ng/mL and a negative MRSI study.

METHODS

A total of 155 men underwent a three-dimensional proton MRSI of the prostate before transrectal ultrasound-guided biopsy for clinical indications. MRSI was performed using an endorectal coil on a 1.5-T magnetic resonance scanner. Patients with no voxels positive for malignancy underwent standard sextant biopsy, and additional MRSI-targeted biopsies were obtained in men with suspicious or malignant voxels. Patients with a biopsy negative for cancer underwent repeat serum PSA estimation every 6 months for a minimum of 18 months.

RESULTS

Of the 155 men, 36 (mean PSA level of 6.47 ng/mL, range 4.25 to 9.9) had no malignant voxels on MRSI. None of them were positive for cancer on biopsy. Of these 36 men, 26 completed at least 18 months (mean 26.9, range 18 to 44) of follow-up. Four patients required repeat biopsies and one, with a persistently elevated PSA level was diagnosed with prostate cancer 29 months after the initial MRSI.

CONCLUSIONS

The results of our study have shown that prostate biopsy can be deferred in patients with an increased serum PSA of 4 to 10 ng/mL if their MRSI does not show any malignant voxels.