Transperineal in-bore 3-T MR imaging-guided prostate biopsy: a prospective clinical observational study

Segmented diffusion-weighted imaging of the prostate: Application to transperineal in-bore 3T MR image-guided targeted biopsy

OBJECTIVE

This study aims to evaluate the applicability of using single-shot and multi-shot segmented diffusion-weighted imaging (DWI) techniques to support biopsy target localization in a cohort of targeted MRI-guided prostate biopsy patients.

MATERIALS AND METHODS

Single-shot echo-planar diffusion-weighted imaging (SS-DWI) and multi-shot segmented (MS-DWI) were performed intra-procedurally on a 3Tesla system in a total of 35 men, who underwent in-bore prostate biopsy inside the scanner bore. Comparisons between SS-DWI and MS-DWI were performed with (in 16 men) and without (in 19 men) parallel coil acceleration (iPAT) for SS-DWI. Overall image quality and artifacts were scored by a radiologist and scores were compared with the Wilcoxon-Mann-Whitney rank test. Correlation between the presence of air and image quality scores was evaluated with Spearman statistics. To quantify distortion, the anteroposterior prostate dimension was measured in SS and MS b=0 diffusion- and T2-weighted images. Signal-to-noise ratio was estimated in a phantom experiment. Agreement and accuracy of targeting based on retrospective localization of restricted diffusion areas in DWI was evaluated with respect to the targets identified using multi-parametric MRI (mpMRI).

RESULTS

Compared to SS-DWI without iPAT, the average image quality score in MS-DWI improved from 2.0 to 3.3 (p<0.005) and the artifact score improved from 2.3 to 1.4 (p<0.005). When iPAT was used in SS-DWI, the average image quality score in MS-DWI improved from 2.6 to 3.3 (p<0.05) and the artifact score improved from 2.1 to 1.4 (p<0.01). Image quality (ρ=-0.74, p<0.0005) and artifact scores (ρ=0.77, p<0.0005) both showed strong correlation with the presence of air in the rectum for the SS-DWI sequence without iPAT. These correlations remained significant when iPAT was enabled (ρ=-0.52, p<0.05 and ρ=0.64, p<0.01). For the comparison MS-DWI vs SS-DWI without iPAT, median differences between diffusion- and T2-weighted image gland measurements were 1.1(0.03-10.4)mm and 4.4(0.5-22.7)mm, respectively. In the SS-DWI-iPAT cohort, median gland dimension differences were 2.7(0.4-5.9)mm and 4.2(0.7-8.9)mm, respectively. Out of the total of 89 targets identified in mpMRI, 20 had corresponding restricted diffusion areas in SS-DWI and 28 in MS-DWI. No statistically significant difference was observed between the distances for the targets in the target-concordant SS- and MS-DWI restricted diffusion areas (5.5mm in SS-DWI vs 4.5mm in MS-DWI, p>0.05).

CONCLUSIONS

MS-DWI applied to prostate imaging leads to a significant reduction of image distortion in comparison with SS-DWI. There is no sufficient evidence however to suggest that intra-procedural DWI can serve as a replacement for tracking of the targets identified in mpMRI for the purposes of targeted MRI-guided prostate biopsy.

In-bore magnetic resonance-guided transrectal biopsy for the detection of clinically significant prostate cancer

PURPOSE

To determine the safety and efficacy of in-bore magnetic resonance-guided prostate biopsy (MRGB) for detection of clinically significant disease (CSD) in untreated men with known or suspected prostate cancer (PCa).

METHODS

512 patients underwent multiparametric magnetic resonance imaging (Mp-MRI) followed by MRGB at one of three centers in this IRB-approved, HIPAA-compliant, retrospective study. Exclusion criteria were prior prostate cancer therapy and incomplete Mp-MRI (n = 51). Patients (n = 461) were analyzed in two subcohorts: no prior PCa (NP) (n = 381) and active surveillance (AS) (n = 80). Detection rates of PCa and CSD (Gleason Score ≥3 + 4) were calculated and compared among subcohorts and by Mp-MRI assessment grade. Logistic regression was performed to identify predictors for detection of PCa and CSD.

RESULTS

Mean patient age was 66 years, median prostate-specific antigen (PSA) was 7.5 ng/mL, and median prostate volume was 54 cc. A mean of 1.7 targets was sampled per gland. Significant adverse events (urosepsis and hematuria with obstruction) occurred in 1% (5/461). Overall PCa detection rates were 51% per patient (233/461) and 37% per lesion (282/757). 65% (151/233) of men with detected PCa had CSD. Per-patient PCa detection rates in the NP and AS subcohorts were 47% (178/381) and 69% (55/80), respectively, significantly higher in the AS group (p < 0.001). CSD was detected in 10% (47/451), 43% (96/225) and 84% (68/81) of lesions with Mp-MRI assessment grades of 3, 4, and 5, respectively. Older age, higher PSA, and lower prostate volume predicted MRGB detection of CSD (OR 1.07 and p = 0.003, OR 1.1 and p = 0.014, and OR 0.98 and p = 0.032, respectively).

CONCLUSIONS

In-bore MRGB is safe and high yield for detection of CSD.

Targeted prostate biopsy and MR-guided therapy for prostate cancer

Prostate cancer is the most commonly diagnosed noncutaneous cancer and second-leading cause of death in men. Many patients with clinically organ-confined prostate cancer undergo definitive treatment of the whole gland including radical prostatectomy, radiation therapy, and cryosurgery. Active surveillance is a growing alternative option for patients with documented low-volume, low-grade prostate cancer. With recent advances in software and hardware of MRI, multiparametric MRI of the prostate has been shown to improve the accuracy in detecting and characterizing clinically significant prostate cancer. Targeted biopsy is increasingly utilized to improve the yield of MR-detected, clinically significant prostate cancer and to decrease in detection of indolent prostate cancer. MR-guided targeted biopsy techniques include cognitive MR fusion TRUS biopsy, in-bore transrectal targeted biopsy using robotic transrectal device, and in-bore direct MR-guided transperineal biopsy with a software-based transperineal grid template. In addition, advances in MR compatible thermal ablation technology allow accurate focal or regional delivery of optimal thermal energy to the biopsy-proved, MRI-detected tumor, utilizing cryoablation, laser ablation, high-intensity focused ultrasound ablation under MR guidance and real-time or near simultaneous monitoring of the ablation zone. Herein we present a contemporary review of MR-guided targeted biopsy techniques of MR-detected lesions as well as MR-guided focal or regional thermal ablative therapies for localized naïve and recurrent cancerous foci of the prostate.

Open-Source Platform for Prostate Motion Tracking During in-Bore Targeted MRI-Guided Biopsy

Accurate sampling of cancer suspicious locations is critical in targeted prostate biopsy, but can be complicated by the motion of the prostate. We present an open-source software for intra-procedural tracking of the prostate and biopsy targets using deformable image registration. The software is implemented in 3D Slicer and is intended for clinical users. We evaluated accuracy, computation time and sensitivity to initialization, and compared implementations that use different versions of the Insight Segmentation Toolkit (ITK). Our retrospective evaluation used data from 25 in-bore MRI-guided prostate biopsy cases (343 registrations total). Prostate Dice similarity coefficient improved on average by 0.17 (p < 0.0001, range 0.02-0.48). Registration was not sensitive to operator variability. Computation time decreased significantly for the implementation using the latest version of ITK. In conclusion, we presented a fully functional open-source tool that is ready for prospective evaluation during clinical MRI-guided prostate biopsy interventions.

Active surveillance for prostate cancer: can we modernize contemporary protocols to improve patient selection and outcomes in the focal therapy era?

PURPOSE OF REVIEW

In the absence of whole gland treatment for prostate cancer, both active surveillance and focal therapy share the common need of requiring a more thorough, detailed and precise analysis of the biological threats within the prostatic parenchyma if one chooses to monitor or selectively eradicate only specific neoplastic targets. In addition, focal therapy utilizes active surveillance post-treatment to monitor the untreated sectors of the prostate. We aim to evaluate the current modalities available to modernize active surveillance protocols in order to distinguish patients who may be safely observed from those who require intervention.

RECENT FINDINGS

Traditional active surveillance protocols by today's standards are rudimentary given the rapidly evolving technologies now available to clinicians. There is growing evidence for the adoption and use of multiparametric MRI and MRI-targeted biopsy to identify and localize prostate cancers of higher stage and grade. In addition, serum markers and prostate tissue DNA, RNA and methylation markers provide novel information that extends beyond Gleason grade to better characterize and define prostate cancer prognosis. Current active surveillance protocols should incorporate these modalities to improve patient stratification to surveillance, focal or whole gland interventions.

SUMMARY

Active surveillance protocols should be modernized to include cancer localization modalities and molecular prognostic markers to improve tumour characterization and better stratify men to surveillance, focal or radical intervention.

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.

Novel Imaging of Prostate Cancer with MRI, MRI/US, and PET

Imaging of prostate cancer presents many challenges to the imaging community. There has been much progress in this space in large part due to MRI and PET radiopharmaceuticals. Though MRI has been focused on the evaluation of local disease and PET on the detection of metastatic disease, these two areas do converge and will be complementary especially with the growth of new PET/MRI technologies. In this review article, we review novel MRI, MRI/US, and PET radiopharmaceuticals which will offer insight into the future direction of imaging in 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.

Likert score 3 prostate lesions: Association between whole-lesion ADC metrics and pathologic findings at MRI/ultrasound fusion targeted biopsy

BACKGROUND

To assess associations between whole-lesion apparent diffusion coefficient (ADC) metrics and pathologic findings of Likert score 3 prostate lesions at MRI/ultrasound fusion targeted biopsy.

METHODS

This retrospective Institutional Review Board-approved study received a waiver of consent. We identified patients receiving a highest lesion score of 3 on 3 Tesla multiparametric MRI reviewed by a single experienced radiologist using a 5-point Likert scale and who underwent fusion biopsy. A total of 188 score 3 lesions in 158 patients were included. Three-dimensional volumes-of-interest encompassing each lesion were traced on ADC maps. Logistic regression was used to predict biopsy results based on whole-lesion ADC metrics and patient biopsy history. Biopsy yield was compared between metrics.

RESULTS

By lesion, targeted biopsy identified tumor in 22.3% and Gleason score (GS) > 6 tumor in 8.5%, although results varied by biopsy history: biopsy-naïve (n = 80), 20.0%/8.8%; prior negative biopsy (n = 53), 9.4%/1.9%; prior positive biopsy (n = 55): 40.0%/14.5%. Biopsy history, whole-lesion mean ADC, whole-lesion ADC10-25 , and whole-lesion ADC25-50 were each significantly associated with tumor or GS > 6 tumor at fusion biopsy (P ≤ 0.047). In men without prior negative prostate biopsy, whole-lesion ADC25-50  ≤ 1.04*10(-3) mm2 /s achieved 90.0% sensitivity and 50.0% specificity for GS > 6 tumor, which was significantly higher (P < 0.001) than specificity of PSA (17.5%) at identical sensitivity.

CONCLUSION

For score 3 lesions in patients without prior negative biopsy, whole-lesion ADC metrics help detect GS > 6 cancer while avoiding negative biopsies. However, deferral of fusion biopsy may be considered for score 3 lesions in patients with prior negative biopsy (without applying whole-lesion ADC metrics) given exceedingly low (∼ 2%) frequency of GS > 6 tumor in this group.

Relationship Between Prebiopsy Multiparametric Magnetic Resonance Imaging (MRI), Biopsy Indication, and MRI-ultrasound Fusion-targeted Prostate Biopsy Outcomes

BACKGROUND

Increasing evidence supports the use of magnetic resonance imaging (MRI)-ultrasound fusion-targeted prostate biopsy (MRF-TB) to improve the detection of clinically significant prostate cancer (PCa) while limiting detection of indolent disease compared to systematic 12-core biopsy (SB).

OBJECTIVE

To compare MRF-TB and SB results and investigate the relationship between biopsy outcomes and prebiopsy MRI.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective analysis of a prospectively acquired cohort of men presenting for prostate biopsy over a 26-mo period. A total of 601 of 803 consecutively eligible men were included.

INTERVENTIONS

All men were offered prebiopsy MRI and assigned a maximum MRI suspicion score (mSS). Men with an MRI abnormality underwent combined MRF-TB and SB.

OUTCOMES

Detection rates for all PCa and high-grade PCa (Gleason score [GS] ≥7) were compared using the McNemar test.

RESULTS AND LIMITATIONS

MRF-TB detected fewer GS 6 PCas (75 vs 121; p<0.001) and more GS ≥7 PCas (158 vs 117; p<0.001) than SB. Higher mSS was associated with higher detection of GS ≥7 PCa (p<0.001) but was not correlated with detection of GS 6 PCa. Prediction of GS ≥7 disease by mSS varied according to biopsy history. Compared to SB, MRF-TB identified more GS ≥7 PCas in men with no prior biopsy (88 vs 72; p=0.012), in men with a prior negative biopsy (28 vs 16; p=0.010), and in men with a prior cancer diagnosis (42 vs 29; p=0.043). MRF-TB detected fewer GS 6 PCas in men with no prior biopsy (32 vs 60; p<0.001) and men with prior cancer (30 vs 46; p=0.034). Limitations include the retrospective design and the potential for selection bias given a referral population.

CONCLUSIONS

MRF-TB detects more high-grade PCas than SB while limiting detection of GS 6 PCa in men presenting for prostate biopsy. These findings suggest that prebiopsy multiparametric MRI and MRF-TB should be considered for all men undergoing prostate biopsy. In addition, mSS in conjunction with biopsy indications may ultimately help in identifying men at low risk of high-grade cancer for whom prostate biopsy may not be warranted.

PATIENT SUMMARY

We examined how magnetic resonance imaging (MRI)-targeted prostate biopsy compares to traditional systematic biopsy in detecting prostate cancer among men with suspicion of prostate cancer. We found that MRI-targeted biopsy detected more high-grade cancers than systematic biopsy, and that MRI performed before biopsy can predict the risk of high-grade cancer.

Open-source image registration for MRI-TRUS fusion-guided prostate interventions

PURPOSE

We propose two software tools for non-rigid registration of MRI and transrectal ultrasound (TRUS) images of the prostate. Our ultimate goal is to develop an open-source solution to support MRI-TRUS fusion image guidance of prostate interventions, such as targeted biopsy for prostate cancer detection and focal therapy. It is widely hypothesized that image registration is an essential component in such systems.

METHODS

The two non-rigid registration methods are: (1) a deformable registration of the prostate segmentation distance maps with B-spline regularization and (2) a finite element-based deformable registration of the segmentation surfaces in the presence of partial data. We evaluate the methods retrospectively using clinical patient image data collected during standard clinical procedures. Computation time and Target Registration Error (TRE) calculated at the expert-identified anatomical landmarks were used as quantitative measures for the evaluation.

RESULTS

The presented image registration tools were capable of completing deformable registration computation within 5 min. Average TRE was approximately 3 mm for both methods, which is comparable with the slice thickness in our MRI data. Both tools are available under nonrestrictive open-source license.

CONCLUSIONS

We release open-source tools that may be used for registration during MRI-TRUS-guided prostate interventions. Our tools implement novel registration approaches and produce acceptable registration results. We believe these tools will lower the barriers in development and deployment of interventional research solutions and facilitate comparison with similar tools.

3T MR-guided in-bore transperineal prostate biopsy: A comparison of robotic and manual needle-guidance templates

PURPOSE

To demonstrate the utility of a robotic needle-guidance template device as compared to a manual template for in-bore 3T transperineal magnetic resonance imaging (MRI)-guided prostate biopsy.

MATERIALS AND METHODS

This two-arm mixed retrospective-prospective study included 99 cases of targeted transperineal prostate biopsies. The biopsy needles were aimed at suspicious foci noted on multiparametric 3T MRI using manual template (historical control) as compared with a robotic template. The following data were obtained: the accuracy of average and closest needle placement to the focus, histologic yield, percentage of cancer volume in positive core samples, complication rate, and time to complete the procedure.

RESULTS

In all, 56 cases were performed using the manual template and 43 cases were performed using the robotic template. The mean accuracy of the best needle placement attempt was higher in the robotic group (2.39 mm) than the manual group (3.71 mm, P < 0.027). The mean core procedure time was shorter in the robotic (90.82 min) than the manual group (100.63 min, P < 0.030). Percentage of cancer volume in positive core samples was higher in the robotic group (P < 0.001). Cancer yields and complication rates were not statistically different between the two subgroups (P = 0.557 and P = 0.172, respectively).

CONCLUSION

The robotic needle-guidance template helps accurate placement of biopsy needles in MRI-guided core biopsy of prostate cancer.

Multimodal imaging for improved diagnosis and treatment of cancers

The authors review methods for image-guided diagnosis and therapy that increase precision in the detection, characterization, and localization of many forms of cancer to achieve optimal target definition and complete resection or ablation. A new model of translational, clinical, image-guided therapy research is presented, and the Advanced Multimodality Image-Guided Operating (AMIGO) suite is described. AMIGO was conceived and designed to allow for the full integration of imaging in cancer diagnosis and treatment. Examples are drawn from over 500 procedures performed on brain, neck, spine, thorax (breast, lung), and pelvis (prostate and gynecologic) areas and are used to describe how they address some of the many challenges of treating brain, prostate, and lung tumors. Cancer 2015;121:817-827. © 2014 American Cancer Society.