Image-directed, tissue-preserving focal therapy of prostate cancer: a feasibility study of a novel deformable magnetic resonance-ultrasound (MR-US) registration system

Meta-Learning Initializations for Interactive Medical Image Registration

We present a meta-learning framework for interactive medical image registration. Our proposed framework comprises three components: a learning-based medical image registration algorithm, a form of user interaction that refines registration at inference, and a meta-learning protocol that learns a rapidly adaptable network initialization. This paper describes a specific algorithm that implements the registration, interaction and meta-learning protocol for our exemplar clinical application: registration of magnetic resonance (MR) imaging to interactively acquired, sparsely-sampled transrectal ultrasound (TRUS) images. Our approach obtains comparable registration error (4.26 mm) to the best-performing non-interactive learning-based 3D-to-3D method (3.97 mm) while requiring only a fraction of the data, and occurring in real-time during acquisition. Applying sparsely sampled data to non-interactive methods yields higher registration errors (6.26 mm), demonstrating the effectiveness of interactive MR-TRUS registration, which may be applied intraoperatively given the real-time nature of the adaptation process.

The ReIMAGINE prostate cancer risk study protocol: A prospective cohort study in men with a suspicion of prostate cancer who are referred onto an MRI-based diagnostic pathway with donation of tissue, blood and urine for biomarker analyses

INTRODUCTION

The ReIMAGINE Consortium was conceived to develop risk-stratification models that might incorporate the full range of novel prostate cancer (PCa) diagnostics (both commercial and academic).

METHODS

ReIMAGINE Risk is an ethics approved (19/LO/1128) multicentre, prospective, observational cohort study which will recruit 1000 treatment-naive men undergoing a multi-parametric MRI (mpMRI) due to an elevated PSA (≤20ng/ml) or abnormal prostate examination who subsequently had a suspicious mpMRI (score≥3, stage ≤T3bN0M0). Primary outcomes include the detection of ≥Gleason 7 PCa at baseline and time to clinical progression, metastasis and death. Baseline blood, urine, and biopsy cores for fresh prostate tissue samples (2 targeted and 1 non-targeted) will be biobanked for future analysis. High-resolution scanning of pathology whole-slide imaging and MRI-DICOM images will be collected. Consortium partners will be granted access to data and biobanks to develop and validate biomarkers using correlation to mpMRI, biopsy-based disease status and long-term clinical outcomes.

RESULTS

Recruitment began in September 2019(n = 533). A first site opened in September 2019 (n = 296), a second in November 2019 (n = 210) and a third in December 2020 (n = 27). Acceptance to the study has been 65% and a mean of 36.5ml(SD+/-10.0), 12.9ml(SD+/-3.7) and 2.8ml(SD+/-0.7) urine, plasma and serum donated for research, respectively. There are currently 4 academic and 15 commercial partners spanning imaging (~9 radiomics, artificial intelligence/machine learning), fluidic (~3 blood-based and ~2urine-based) and tissue-based (~1) biomarkers.

CONCLUSION

The consortium will develop, or adjust, risk models for PCa, and provide a platform for evaluating the role of novel diagnostics in the era of pre-biopsy MRI and targeted biopsy.

Real-time multimodal image registration with partial intraoperative point-set data

We present Free Point Transformer (FPT) - a deep neural network architecture for non-rigid point-set registration. Consisting of two modules, a global feature extraction module and a point transformation module, FPT does not assume explicit constraints based on point vicinity, thereby overcoming a common requirement of previous learning-based point-set registration methods. FPT is designed to accept unordered and unstructured point-sets with a variable number of points and uses a "model-free" approach without heuristic constraints. Training FPT is flexible and involves minimizing an intuitive unsupervised loss function, but supervised, semi-supervised, and partially- or weakly-supervised training are also supported. This flexibility makes FPT amenable to multimodal image registration problems where the ground-truth deformations are difficult or impossible to measure. In this paper, we demonstrate the application of FPT to non-rigid registration of prostate magnetic resonance (MR) imaging and sparsely-sampled transrectal ultrasound (TRUS) images. The registration errors were 4.71 mm and 4.81 mm for complete TRUS imaging and sparsely-sampled TRUS imaging, respectively. The results indicate superior accuracy to the alternative rigid and non-rigid registration algorithms tested and substantially lower computation time. The rapid inference possible with FPT makes it particularly suitable for applications where real-time registration is beneficial.

Histology to 3D in vivo MR registration for volumetric evaluation of MRgFUS treatment assessment biomarkers

Advances in imaging and early cancer detection have increased interest in magnetic resonance (MR) guided focused ultrasound (MRgFUS) technologies for cancer treatment. MRgFUS ablation treatments could reduce surgical risks, preserve organ tissue and function, and improve patient quality of life. However, surgical resection and histological analysis remain the gold standard to assess cancer treatment response. For non-invasive ablation therapies such as MRgFUS, the treatment response must be determined through MR imaging biomarkers. However, current MR biomarkers are inconclusive and have not been rigorously evaluated against histology via accurate registration. Existing registration methods rely on anatomical features to directly register in vivo MR and histology. For MRgFUS applications in anatomies such as liver, kidney, or breast, anatomical features that are not caused by the treatment are often insufficient to drive direct registration. We present a novel MR to histology registration workflow that utilizes intermediate imaging and does not rely on anatomical MR features being visible in histology. The presented workflow yields an overall registration accuracy of 1.00 ± 0.13 mm. The developed registration pipeline is used to evaluate a common MRgFUS treatment assessment biomarker against histology. Evaluating MR biomarkers against histology using this registration pipeline will facilitate validating novel MRgFUS biomarkers to improve treatment assessment without surgical intervention. While the presented registration technique has been evaluated in a MRgFUS ablation treatment model, this technique could be potentially applied in any tissue to evaluate a variety of therapeutic options.

Usability and diagnostic accuracy of different MRI/ultrasound-guided fusion biopsy systems for the detection of clinically significant and insignificant prostate cancer: a prospective cohort study

PURPOSE

To explore the usability and diagnostic accuracy for prostate cancer of three multiparametric magnetic resonance imaging (mpMRI)/transrectal ultrasound (TRUS)-guided fusion biopsy systems operated by the same urologists.

METHODS

We performed a prospective, observational study including patients that underwent prostate biopsy due to a visible lesion in mpMRI (PI-RADS ≥ 3). We consecutively assessed two platforms with a rigid image registration (BioJet, D&K Technologies and UroNav, Invivo Corporation) and one with an elastic registration (Trinity, KOELIS). Four urologists evaluated each fusion system in terms of usability based on the System Usability Scale and diagnostic accuracy based on the detection of prostate cancer.

RESULTS

We enrolled 60 consecutive patients that received mpMRI/TRUS-guided prostate biopsy with the BioJet (n = 20), UroNav (n = 20) or Trinity (n = 20) fusion system. Comparing the rigid with the elastic registration systems, the rigid registration systems were more user-friendly compared to the elastic registration systems (p = 0.012). Similarly, the prostate biopsy with the rigid registration systems had a shorter duration compared to the elastic registration system (p < 0.001). Overall, 40 cases of prostate cancer were detected. Of them, both the BioJet and UroNav fusion systems detected 13 prostate cancer cases, while the Trinity detected 14. No significant differences were demonstrated among the three fusion biopsy systems in terms of highest ISUP Grade Group (p > 0.99).

CONCLUSIONS

Rigid fusion biopsy systems are easier to use and provide shorter operative time compared to elastic systems, while both types of platforms display similar detection rates for prostate cancer. Still, further high-quality, long-term results are mandatory.

Biomechanically constrained non-rigid MR-TRUS prostate registration using deep learning based 3D point cloud matching

A non-rigid MR-TRUS image registration framework is proposed for prostate interventions. The registration framework consists of a convolutional neural networks (CNN) for MR prostate segmentation, a CNN for TRUS prostate segmentation and a point-cloud based network for rapid 3D point cloud matching. Volumetric prostate point clouds were generated from the segmented prostate masks using tetrahedron meshing. The point cloud matching network was trained using deformation field that was generated by finite element analysis. Therefore, the network implicitly models the underlying biomechanical constraint when performing point cloud matching. A total of 50 patients' datasets were used for the network training and testing. Alignment of prostate shapes after registration was evaluated using three metrics including Dice similarity coefficient (DSC), mean surface distance (MSD) and Hausdorff distance (HD). Internal point-to-point registration accuracy was assessed using target registration error (TRE). Jacobian determinant and strain tensors of the predicted deformation field were calculated to analyze the physical fidelity of the deformation field. On average, the mean and standard deviation were 0.94±0.02, 0.90±0.23 mm, 2.96±1.00 mm and 1.57±0.77 mm for DSC, MSD, HD and TRE, respectively. Robustness of our method to point cloud noise was evaluated by adding different levels of noise to the query point clouds. Our results demonstrated that the proposed method could rapidly perform MR-TRUS image registration with good registration accuracy and robustness.

Use of the IDEAL framework in the urological literature: where are we in 2018?

OBJECTIVES

To assess uptake and application of the IDEAL principles in original surgical procedure- or device-related clinical research studies, as well as its reported relevance as characterized by secondary publications, editorials and reviews.

MATERIALS AND METHODS

IDEAL (Idea, Development, Exploration, Assessment, Long-term study) is a framework that provides stage-specific guidance for surgical innovation and represented a major advance towards raising evidential standards. We performed a comprehensive literature search of all urology-related publications citing one or more of seven key publications on IDEAL in The Lancet and BMJ using multiple databases up to 31 December 2017.

RESULTS

We identified a total of 150 urology-related manuscripts citing IDEAL, of which 83 (55.3%) were original research and 67 (44.7%) were secondary publications. Among the original research articles, 40 (48.2%) did not explicitly apply IDEAL principles or were not surgical innovation studies. The IDEAL phases of the 43 (51.8%) remaining original research studies were IDEAL, in nine (20.9%), 27 (62.8%), four (9.3%), 0 (0%), and three publications (7.0%), respectively. Across IDEAL stages, 30 (75.0%) studies were prospective, 29 (85.3%) reported ethical oversight, and 39 (90.7%) captured treatment-related harms. None of the studies collected information on physician experience.

CONCLUSIONS

The IDEAL framework has found widespread adoption in the urology literature as witnessed by a large number of original manuscripts and secondary publications citing IDEAL; however, its application is largely limited to the early stages of surgical innovation, frequently with inappropriate and incomplete implementation. Further efforts are needed to guide investigators in the optimal use of the IDEAL framework as it relates to surgical innovation in urology.

Focal therapy for localized prostate cancer: is there a "middle ground" between active surveillance and definitive treatment?

In recent years, it has come a long way in the diagnosis, treatment, and follow-up of prostate cancer. Beside this, it was argued that definitive treatments could cause overtreatment, particularly in the very low, low, and favorable risk group. When alternative treatment and follow-up methods are being considered for this group of patients, active surveillance is seen as a good alternative for patients with very low and low-risk groups in this era. However, it has become necessary to find other alternatives for patients in the favorable risk group or patients who cannot adopt active follow-up. In the light of technological developments, the concept of focal therapy was introduced with the intensification of research to treat only the lesioned area instead of treating the entire organ for prostate lesions though there are not many publications about many of them yet. According to the initial results, it was understood that the results could be good if the appropriate focal therapy technique was applied to the appropriate patient. Thus, focal therapies have begun to find their "middle ground" place between definitive therapies and active follow-up.

Appraising the uptake and use of the IDEAL Framework and Recommendations: A review of the literature

INTRODUCTION

Evaluation of new surgical innovations is complex and variably regulated, and historically the quality of surgical studies has been criticized. The IDEAL (Idea, Development, Exploration, Assessment, Long-term monitoring) Framework was established to provide a pathway for evaluating surgical innovations at each stage of their development in order to produce high quality surgical research. Since the inception of IDEAL in 2009, there has been no assessment of its use. In this review, we look at the uptake and usage of IDEAL by examining the published literature.

METHODS

We conducted a literature search to identify all of the publications that cited IDEAL and included only those papers that intentionally used IDEAL as part of the study methodology. We then characterized these publications by year of publication, specialty, and geographical location. We performed a critical appraisal of Stage 1, 2a, and 2b studies in order to assess the degree to which authors have correctly followed the Framework and Recommendations.

RESULTS

We found 790 citations of IDEAL publications, and after abstract and full-text screening, 38 prospective studies for a surgical innovation that used IDEAL remained. We saw an overall increase in the uptake of IDEAL, with a predominance in urology and origin in the United Kingdom. The critical appraisal showed that although authors identified their project as using IDEAL, they often failed to include key IDEAL characteristics; this was especially true for the features unique to IDEAL Stages 2a and 2b.

CONCLUSION

It is evident from the large number of studies citing IDEAL that the importance and challenges of reporting surgical research is well recognized among researchers. There is growing enthusiasm for using IDEAL but the current level of understanding of the Recommendations is low. Clearer and more comprehensive explanation of the application of the IDEAL Framework and Recommendations is needed to guide surgical researchers undertaking IDEAL based studies of surgical innovations.

Comparison of Elastic and Rigid Registration during Magnetic Resonance Imaging/Ultrasound Fusion-Guided Prostate Biopsy: A Multi-Operator Phantom Study

PURPOSE

The relative value of rigid or elastic registration during magnetic resonance imaging/ultrasound fusion guided prostate biopsy has been poorly studied. We compared registration errors (the distance between a region of interest and fiducial markers) between rigid and elastic registration during fusion guided prostate biopsy using a prostate phantom model.

MATERIALS AND METHODS

Four gold fiducial markers visible on magnetic resonance imaging and ultrasound were placed throughout 1 phantom prostate model. The phantom underwent magnetic resonance imaging and the fiducial markers were labeled as regions of interest. An experienced user and a novice user of fusion guided prostate biopsy targeted regions of interest and then the corresponding fiducial markers on ultrasound after rigid and then elastic registration. Registration errors were compared.

RESULTS

A total of 224 registration error measurements were recorded. Overall elastic registration did not provide significantly improved registration error over rigid registration (mean ± SD 4.87 ± 3.50 vs 4.11 ± 2.09 mm, p = 0.05). However, lesions near the edge of the phantom showed increased registration errors when using elastic registration (5.70 ± 3.43 vs 3.23 ± 1.68 mm, p = 0.03). Compared to the novice user the experienced user reported decreased registration error with rigid registration (3.25 ± 1.49 vs 4.98 ± 2.10 mm, p <0.01) and elastic registration (3.94 ± 2.61 vs 6.07 ± 4.16 mm, p <0.01).

CONCLUSIONS

We found no difference in registration errors between rigid and elastic registration overall but rigid registration decreased the registration error of targets near the prostate edge. Additionally, operator experience reduced registration errors regardless of the registration method. Therefore, elastic registration algorithms cannot serve as a replacement for attention to detail during the registration process and anatomical landmarks indicating accurate registration when beginning the procedure and before targeting each region of interest.

MRI-TRUS fusion for electrode positioning during irreversible electroporation for treatment of prostate cancer

We aimed to introduce an approach for image-guided positioning of electrodes for irreversible electroporation (IRE) in patients with prostate cancer using a magnetic resonance imaging-transrectal ultrasonography (MRI-TRUS) fusion technique. In 10 consecutive patients with biopsy-proven Gleason score ≤3+4 prostate cancer, 19 G electrodes were inserted into the prostate using a transperineal access. Magnetic resonance images of the prostate acquired before IRE were fused with transrectal ultrasound images acquired during IRE. The position of the ultrasound probe was tracked via a sensor and corresponding magnetic resonance images were calculated in real-time. While MRI allowed delineation of the target volume, the position of the electrodes could be visualized on ultrasound images; the distance between individual electrode pairs was measured. Based on these measurements the software installed on the IRE unit was able to calculate the voltage necessary to generate the electric field for ablation. Using contrast-enhanced ultrasound, changes in perfusion within the ablation zone after IRE were documented. This technique allowed positioning of the electrodes around the target volume under image guidance in all patients treated with IRE. The target lesion and a safety margin were covered within the estimated ablation zone. MRI-TRUS guidance for IRE combines the advantages of good visualization of the target lesion on MRI with the ability of ultrasound to acquire imaging in real-time with a mobile device.

Targeted Ablative Therapies for Prostate Cancer

Men diagnosed with low- to intermediate-risk, clinically localized prostate cancer (PCa) often face a daunting and difficult decision with respect to treatment: active surveillance (AS) or radical therapy. This decision is further confounded by the fact that many of these men diagnosed, by an elevated PSA, will have indolent disease and never require intervention. Radical treatments, including radical prostatectomy and whole-gland radiation, offer greater certainty for cancer control, but at the risk of significant urinary and/or sexual morbidity. Conversely, AS preserves genitourinary function and quality of life in exchange for burdensome surveillance and the psychological impact of living with cancer.

Multimodal Imaging in Focal Therapy Planning and Assessment in Primary Prostate Cancer

PURPOSE

There is increasing interest in focal therapy (male lumpectomy) of localized low-intermediate risk prostate cancer. Focal therapy is typically associated with low morbidity and provides the possibility of retreatment. Imaging is pivotal in stratification of men with localized prostate cancer for active surveillance, focal therapy or radical intervention. This article provides a concise review of focal therapy and the evolving role of imaging in this clinical setting.

METHODS

We performed a narrative and critical literature review by searching PubMed/Medline database from January 1997 to January 2017 for articles in the English language and the use of search keywords "focal therapy", "prostate cancer", and "imaging".

RESULTS

Most imaging studies are based on multiparametric magnetic resonance imaging. Transrectal ultrasound is inadequate independently but multiparametric ultrasound may provide new prospects. Positron emission tomography with radiotracers targeted to various underlying tumor biological features may provide unprecedented new opportunities. Multimodal Imaging appears most useful in localization of intraprostatic dominant index lesions amenable to focal therapy, in early assessment of therapeutic efficacy and potential need for additional focal treatments or transition to whole-gland therapy, and in predicting short-term and long-term outcomes.

CONCLUSION

Multimodal imaging is anticipated to play an increasing role in the focal therapy planning and assessment of low-intermediate risk prostate cancer and thereby moving this form of treatment option forward in the clinic.

Learning Non-rigid Deformations for Robust, Constrained Point-based Registration in Image-Guided MR-TRUS Prostate Intervention

Accurate and robust non-rigid registration of pre-procedure magnetic resonance (MR) imaging to intra-procedure trans-rectal ultrasound (TRUS) is critical for image-guided biopsies of prostate cancer. Prostate cancer is one of the most prevalent forms of cancer and the second leading cause of cancer-related death in men in the United States. TRUS-guided biopsy is the current clinical standard for prostate cancer diagnosis and assessment. State-of-the-art, clinical MR-TRUS image fusion relies upon semi-automated segmentations of the prostate in both the MR and the TRUS images to perform non-rigid surface-based registration of the gland. Segmentation of the prostate in TRUS imaging is itself a challenging task and prone to high variability. These segmentation errors can lead to poor registration and subsequently poor localization of biopsy targets, which may result in false-negative cancer detection. In this paper, we present a non-rigid surface registration approach to MR-TRUS fusion based on a statistical deformation model (SDM) of intra-procedural deformations derived from clinical training data. Synthetic validation experiments quantifying registration volume of interest overlaps of the PI-RADS parcellation standard and tests using clinical landmark data demonstrate that our use of an SDM for registration, with median target registration error of 2.98 mm, is significantly more accurate than the current clinical method. Furthermore, we show that the low-dimensional SDM registration results are robust to segmentation errors that are not uncommon in clinical TRUS data.

Development and Phantom Validation of a 3-D-Ultrasound-Guided System for Targeting MRI-Visible Lesions During Transrectal Prostate Biopsy

OBJECTIVE

Three- and four-dimensional transrectal ultrasound transducers are now available from most major ultrasound equipment manufacturers, but currently are incorporated into only one commercial prostate biopsy guidance system. Such transducers offer the benefits of rapid volumetric imaging, but can cause substantial measurement distortion in electromagnetic tracking sensors, which are commonly used to enable 3-D navigation. In this paper, we describe the design, development, and validation of a 3-D-ultrasound-guided transrectal prostate biopsy system that employs high-accuracy optical tracking to localize the ultrasound probe and prostate targets in 3-D physical space.

METHODS

The accuracy of the system was validated by evaluating the targeted needle placement error after inserting a biopsy needle to sample planned targets in a phantom using standard 2-D ultrasound guidance versus real-time 3-D guidance provided by the new system.

RESULTS

The overall mean needle-segment-to-target distance error was 3.6 ± 4.0 mm and mean needle-to-target distance was 3.2 ± 2.4 mm.

CONCLUSION

A significant increase in needle placement accuracy was observed when using the 3-D guidance system compared with visual targeting of invisible (virtual) lesions using a standard B-mode ultrasound-guided biopsy technique.

Focal therapy as primary treatment for localized prostate cancer: definition, needs and future

Focal therapy (FT) may offer a promising treatment option in the field of low to intermediate risk localized prostate cancer. The aim of this concept is to combine minimal morbidity with cancer control as well as maintain the possibility of retreatment. Recent advances in MRI and targeted biopsy has improved the diagnostic pathway of prostate cancer and increased the interest in FT. However, before implementation of FT in routine clinical practice, several challenges are still to overcome including patient selection, treatment planning, post-therapy monitoring and definition of oncologic outcome surrogates. In this article, relevant questions regarding the key steps of FT are critically discussed and the main available energy modalities are analyzed taking into account their advantages and unmet needs.

MR-TRUS Fusion Biopsy

The leading application of multiparametric magnetic resonance imaging (mpMRI) of the prostate is for lesion detection with the intention of tissue sampling (biopsy). Although direct in-bore magnetic resonance (MR)-guided biopsy allows for confirmation of the biopsy site, this can be expensive, time-consuming, and most importantly limited in availability. MR-transrectal ultrasound (MR-TRUS) image fusion targeted biopsy (TBx) allows for lesions identified on MRI to be targeted with the ease, efficiency, and availability of ultrasound.The learning objectives are optimized mpMRI protocol and reporting for image fusion targeted biopsy; methods of TRUS TBx; performance and limitations of MR-TRUS TBx; future improvements and applications.

Multiattribute probabilistic prostate elastic registration (MAPPER): application to fusion of ultrasound and magnetic resonance imaging

PURPOSE

Transrectal ultrasound (TRUS)-guided needle biopsy is the current gold standard for prostate cancer diagnosis. However, up to 40% of prostate cancer lesions appears isoechoic on TRUS. Hence, TRUS-guided biopsy has a high false negative rate for prostate cancer diagnosis. Magnetic resonance imaging (MRI) is better able to distinguish prostate cancer from benign tissue. However, MRI-guided biopsy requires special equipment and training and a longer procedure time. MRI-TRUS fusion, where MRI is acquired preoperatively and then aligned to TRUS, allows for advantages of both modalities to be leveraged during biopsy. MRI-TRUS-guided biopsy increases the yield of cancer positive biopsies. In this work, the authors present multiattribute probabilistic postate elastic registration (MAPPER) to align prostate MRI and TRUS imagery.

METHODS

MAPPER involves (1) segmenting the prostate on MRI, (2) calculating a multiattribute probabilistic map of prostate location on TRUS, and (3) maximizing overlap between the prostate segmentation on MRI and the multiattribute probabilistic map on TRUS, thereby driving registration of MRI onto TRUS. MAPPER represents a significant advancement over the current state-of-the-art as it requires no user interaction during the biopsy procedure by leveraging texture and spatial information to determine the prostate location on TRUS. Although MAPPER requires manual interaction to segment the prostate on MRI, this step is performed prior to biopsy and will not substantially increase biopsy procedure time.

RESULTS

MAPPER was evaluated on 13 patient studies from two independent datasets—Dataset 1 has 6 studies acquired with a side-firing TRUS probe and a 1.5 T pelvic phased-array coil MRI; Dataset 2 has 7 studies acquired with a volumetric end-firing TRUS probe and a 3.0 T endorectal coil MRI. MAPPER has a root-mean-square error (RMSE) for expert selected fiducials of 3.36 ± 1.10 mm for Dataset 1 and 3.14 ± 0.75 mm for Dataset 2. State-of-the-art MRI-TRUS fusion methods report RMSE of 3.06-2.07 mm.

CONCLUSIONS

MAPPER aligns MRI and TRUS imagery without manual intervention ensuring efficient, reproducible registration. MAPPER has a similar RMSE to state-of-the-art methods that require manual intervention.

High intensity focused ultrasound as a tool for tissue engineering: Application to cartilage

This article promotes the use of High Intensity Focused Ultrasound (HIFU) as a tool for affecting the local properties of tissue engineered constructs in vitro. HIFU is a low cost, non-invasive technique used for eliciting focal thermal elevations at variable depths within tissues. HIFU can be used to denature proteins within constructs, leading to decreased permeability and potentially increased local stiffness. Adverse cell viability effects remain restricted to the affected area. The methods described in this article are explored through the scope of articular cartilage tissue engineering and the fabrication of osteochondral constructs, but may be applied to the engineering of a variety of different tissues.

Image-guided focal therapy for prostate cancer

The adoption of routine prostate specific antigen screening has led to the discovery of many small and low-grade prostate cancers which have a low probability of causing mortality. These cancers, however, are often treated with radical therapies resulting in long-term side effects. There has been increasing interest in minimally invasive focal therapies to treat these tumors. While imaging modalities have improved rapidly over the past decade, similar advances in image-guided therapy are now starting to emerge--potentially achieving equivalent oncologic efficacy while avoiding the side effects of conventional radical surgery. The purpose of this article is to review the existing literature regarding the basis of various focal therapy techniques such as cryotherapy, microwave, laser, and high intensity focused ultrasound, and to discuss the results of recent clinical trials that demonstrate early outcomes in patients with prostate cancer.

High Intensity Focused Ultrasound versus Brachytherapy for the Treatment of Localized Prostate Cancer: A Matched-Pair Analysis

Purpose. To evaluate postoperative morbidity and long term oncologic and functional outcomes of high intensity focused ultrasound (HIFU) compared to brachytherapy for the treatment of localized prostate cancer. Material and Methods. Patients treated by brachytherapy were matched 1 : 1 with patients who underwent HIFU. Differences in postoperative complications across the two groups were assessed using Wilcoxon's rank-sum or χ (2) test. Kaplan-Meier curves, log-rank tests, and Cox regression models were constructed to assess differences in survival rates between the two groups. Results. Brachytherapy was significantly associated with lower voiding LUTS and less frequent acute urinary retention (p < 0.05). Median oncologic follow-up was 83 months (13-123 months) in the HIFU cohort and 44 months (13-89 months) in the brachytherapy cohort. Median time to achieve PSA nadir was statistically shorter in the HIFU. Biochemical recurrence-free survival rate was significantly higher in the brachytherapy cohort compared to HIFU cohort (68.5% versus 53%, p < 0.05). No statistically significant difference in metastasis-free, cancer specific, and overall survivals was observed between the two groups. Conclusion. HIFU and brachytherapy are safe with no significant difference in cancer specific survival on long term oncologic follow-up. Nonetheless, a randomized controlled trial is needed to confirm these results.

Transrectal Ultrasound (US), Contrast-enhanced US, Real-time Elastography, HistoScanning, Magnetic Resonance Imaging (MRI), and MRI-US Fusion Biopsy in the Diagnosis of Prostate Cancer

CONTEXT

Debates on overdiagnosis and overtreatment of prostate cancer (PCa) are ongoing and there is still huge uncertainty regarding misclassification of prostate biopsy results. Several imaging techniques that have emerged in recent years could overcome over- and underdiagnosis in PCa.

OBJECTIVE

To review the literature on transrectal ultrasound (TRUS)-based techniques (contrast enhancement, HistoScanning, elastography) and magnetic resonance imaging (MRI)-based techniques for a nonsystematic overview of their benefits and limitations.

EVIDENCE ACQUISITION

A comprehensive search of the PubMed database between August 2004 and August 2014 was performed. Studies assessing grayscale TRUS, contrast-enhanced (CE)-TRUS, elastography, HistoScanning, multiparametric MRI (mpMRI), and MRI-TRUS fusion biopsy were included. Publications before 2004 were included if they reported the principle or the first clinical results for these techniques.

EVIDENCE SYNTHESIS

Grayscale TRUS alone cannot detect PCa foci (detection rate 23-29%). TRUS-based (elastography) and MRI-based techniques (MRI-TRUS fusion biopsy) have significantly improved PCa diagnostics, with sensitivity of 53-74% and specificity of 72-95%. HistoScanning does not provide convincing or homogeneous results (specificity 19-82%). CE-TRUS seems to be user dependent; it is used in a low number of high-volume centers and has wide ranges for sensitivity (54-79%) and specificity (42-95%). For all the techniques reviewed, prospective multicenter studies with consistent definitions are lacking.

CONCLUSIONS

Standard grayscale TRUS is unreliable for PCa detection. Among the techniques reviewed, mpMRI and MRI-TRUS fusion biopsy seem to be suitable for enhancing PCa diagnostics. Elastography shows promising results according to the literature. CE-TRUS yields very inhomogeneous results and might not be the ideal technique for clinical practice. The value of HistoScanning must be questioned according to the literature.

PATIENT SUMMARY

New imaging modalities such as elastography and magnetic resonance imaging/transrectal ultrasound fusion biopsies have improved the detection of prostate cancer. This may lower the burden of overtreatment as a result of more precise diagnosis.

Determination of optimal drug dose and light dose index to achieve minimally invasive focal ablation of localised prostate cancer using WST11-vascular-targeted photodynamic (VTP) therapy

OBJECTIVE

To determine the optimal drug and light dose for prostate ablation using WST11 (TOOKAD Soluble) for vascular-targeted photodynamic (VTP) therapy in men with low-risk prostate cancer.

PATIENTS AND METHODS

In all, 42 men with low-risk prostate cancer were enrolled in the study but two who underwent anaesthesia for the procedure did not receive the drug or light dose. Thus, 40 men received a single dose of 2, 4 or 6 mg/kg WST11 activated by 200 J/cm light at 753 nm. WST11 was given as a 10-min intravenous infusion. The light dose was delivered using cylindrical diffusing fibres within hollow plastic needles positioned in the prostate using transrectal ultrasonography (TRUS) guidance and a brachytherapy template. Magnetic resonance imaging (MRI) was used to assess treatment effect at 7 days, with assessment of urinary function (International Prostate Symptom Score [IPSS]), sexual function (International Index of Erectile Function [IIEF]) and adverse events at 7 days, 1, 3 and 6 months after VTP. TRUS-guided biopsies were taken at 6 months.

RESULTS

In all, 39 of the 40 treated men completed the follow-up. The Day-7 MRI showed maximal treatment effect (95% of the planned treatment volume) in men who had a WST11 dose of 4 mg/kg, light dose of 200 J/cm and light density index (LDI) of >1. In the 12 men treated with these parameters, the negative biopsy rate was 10/12 (83%) at 6 months, compared with 10/26 (45%) for the men who had either a different drug dose (10 men) or an LDI of <1 (16). Transient urinary symptoms were seen in most of the men, with no significant difference in IPSS score between baseline and 6 months after VTP. IIEF scores were not significantly different between baseline and 6 months after VTP.

CONCLUSION

Treatment with 4 mg/kg TOOKAD Soluble activated by 753 nm light at a dose of 200 J/cm and an LDI of >1 resulted in treatment effect in 95% of the planned treatment volume and a negative biopsy rate at 6 months of 10/12 men (83%).

A prospective development study investigating focal irreversible electroporation in men with localised prostate cancer: Nanoknife Electroporation Ablation Trial (NEAT)

Introduction

Focal therapy may reduce the toxicity of current radical treatments while maintaining the oncological benefit. Irreversible electroporation (IRE) has been proposed to be tissue selective and so might have favourable characteristics compared to the currently used prostate ablative technologies. The aim of this trial is to determine the adverse events, genito-urinary side effects and early histological outcomes of focal IRE in men with localised prostate cancer.

Methods

This is a single centre prospective development (stage 2a) study following the IDEAL recommendations for evaluating new surgical procedures. Twenty men who have MRI-visible disease localised in the anterior part of the prostate will be recruited. The sample size permits a precision estimate around key functional outcomes. Inclusion criteria include PSA ≤ 15 ng/ml, Gleason score ≤ 4 + 3, stage T2N0M0 and absence of clinically significant disease outside the treatment area. Treatment delivery will be changed in an adaptive iterative manner so as to allow optimisation of the IRE protocol. After focal IRE, men will be followed during 12 months using validated patient reported outcome measures (IPSS, IIEF-15, UCLA-EPIC, EQ-5D, FACT-P, MAX-PC). Early disease control will be evaluated by mpMRI and targeted transperineal biopsy of the treated area at 6 months.

Discussion

The NEAT trial will assess the early functional and disease control outcome of focal IRE using an adaptive design. Our protocol can provide guidance for designing an adaptive trial to assess new surgical technologies in the challenging landscape of health technology assessment in prostate cancer treatment.

Health technology assessment in evolution - focal therapy in localised prostate cancer

Focal therapy in prostate cancer aims to treat only the part of the gland harboring clinically significant disease while preserving the rest of the tissue. This approach may substantially reduce treatment-related toxicity without compromising disease control outcomes. Short- to medium-term functional and oncological results in prospective interventional studies are promising, but comparative effectiveness research against standard of care is required to incorporate focal therapy among standard options. In this review, we discuss the actual stage of assessment and results of sources of energy commonly used to deliver focal therapy. We also provide our viewpoint on how the field will evolve in the near future.

Single high intensity focused ultrasound session as a whole gland primary treatment for clinically localized prostate cancer: 10-year outcomes

Objectives. To assess the treatment outcomes of a single session of whole gland high intensity focused ultrasound (HIFU) for patients with localized prostate cancer (PCa). Methods. Response rates were defined using the Stuttgart and Phoenix criteria. Complications were graded according to the Clavien score. Results. At a median follow-up of 94months, 48 (44.4%) and 50 (46.3%) patients experienced biochemical recurrence for Phoenix and Stuttgart definition, respectively. The 5- and 10-year actuarial biochemical recurrence free survival rates were 57% and 40%, respectively. The 10-year overall survival rate, cancer specific survival rate, and metastasis free survival rate were 72%, 90%, and 70%, respectively. Preoperative high risk category, Gleason score, preoperative PSA, and postoperative nadir PSA were independent predictors of oncological failure. 24.5% of patients had self-resolving LUTS, 18.2% had urinary tract infection, and 18.2% had acute urinary retention. A grade 3b complication occurred in 27 patients. Pad-free continence rate was 87.9% and the erectile dysfunction rate was 30.8%. Conclusion. Single session HIFU can be alternative therapy for patients with low risk PCa. Patients with intermediate risk should be informed about the need of multiple sessions of HIFU and/or adjuvant treatments and HIFU performed very poorly in high risk patients.

Primary Zonal High Intensity Focused Ultrasound for Prostate Cancer: Results of a Prospective Phase IIa Feasibility Study

OBJECTIVES

To present the results of a prospective phase IIa study assessing the role of primary zonal High Intensity Focused Ultrasound (HIFU) for prostate cancer treatment.

METHODS

31 consecutive patients with unilateral organ confined prostate cancer primarily treated by zonal HIFU (from February 2007 to June 2011) were recruited into a single centre prospective phase IIa feasibility study. Complications were prospectively recorded and graded according to the Clavien-Dindo score. Postoperatively, patients were followed with serial serum PSA determinations and digital rectal examinations. An individual PSA nadir was identified in each patient. Followup also included whole gland biopsies performed in the event of a PSA rising>2.0 ng/mL above nadir value (Phoenix criteria).

RESULTS

At a median followup of 38 months, biochemical recurrence free survival was 100%, 89%, and 82.7% at 1, 2, and 3 years, respectively, with overall and cancer specific survival of 100%. The procedure was safe and well tolerated with no major adverse events. All patients were continent at their last followup and 55.2% (16/29) had erectile function sufficient for penetration.

CONCLUSION

Primary zonal HIFU is a valid focal therapy strategy, safe and feasible in day to day practice with good promising results [corrected].

A multi-centre prospective development study evaluating focal therapy using high intensity focused ultrasound for localised prostate cancer: The INDEX study

INTRODUCTION

Focal therapy offers the possibility of cancer control, without the side effect profile of radical therapies. Early single centre prospective development studies using high intensity focused ultrasound (HIFU) have demonstrated encouraging genitourinary functional preservation and short-term cancer control. Large multi-centre trials are required to evaluate medium-term cancer control and reproduce functional recovery. We describe the study design of an investigator-led UK multi-centre, single arm trial using HIFU to deliver focal therapy for men with localised prostate cancer.

METHODS

One-hundred and forty men with histologically proven localised low or intermediate risk prostate cancer (PSA < 15, Gleason ≤ 7, ≤ T2cN0M0) will undergo precise characterisation of the prostate using a combination of multi-parametric (mp)MRI and transperineal template prostate mapping (TPM) biopsies. Unilateral dominant tumours, the so-called index lesion, will be eligible for treatment provided the contra-lateral side is free of 'clinically significant' disease (as defined by Gleason ≥ 7 or maximum cancer core length ≥4 mm). Patients will receive focal therapy using HIFU (Sonablate 500®). Treatment effect will be assessed by targeted biopsies of the treated area and TPM biopsies at 36-months.

RESULTS

Primary outcome is the absence of clinically significant disease based on 36-month post-treatment TPM biopsies. Secondary outcomes address a) genitourinary function using validated patient questionnaires (IPSS, IPSS-QoL, IIEF-15, EPIC-Urinary, EPIC-Bowel, FACT-P, EQ-5D), b) the predictive validity of imaging, and c) risk factors for treatment failure.

CONCLUSIONS

INDEX will be the first multi-centre, medium term follow-up trial to evaluate the outcomes of a tissue preserving strategy for men with localised prostate cancer using the TPM-ablate-TPM strategy.