Advancements ın Prostate Cancer Dıagnosıs: Prostate MRI/TRUS Fusıon Bıopsy

Table of Contents

Advancements ın Prostate Cancer Dıagnosıs: Prostate MRI/TRUS Fusıon Bıopsy

Moreover, the screening may detect prostate cancer which is associated with aggressive biology so that the patients could seek treatments that are not beneficial to them. The Clinically localized prostate cancer (cLPCa) is usually initially detected by the biopsy of the prostate. Indeed, TRUS-guided prostate biopsy is the standard protocol for the detection of cLPCa, and systematic random biopsies are performed based on standard sector protocols. Nonetheless, the overall accuracy of systematic biopsy for the detection of image-estimated index tumors is only approximately 50%, and the primary sextant of the biopsy does not provide any data on tumor localization or aggressiveness.

Prostate cancer is the leading cause of noncutaneous cancer in males. The American Cancer Society and the 2017 National Comprehensive Cancer Network guidelines recommend prostate cancer screening should start at the age of 50 for an average-risk male with a life expectancy of at least 10 to 15 years, and earlier screening at the age of 45 should also be considered for an individual with an increased risk of prostate cancer (i.e., African American). The prostate-specific antigen test has been widely used for prostate cancer detection and management, but the serum prostate-specific antigen test has a low specificity, resulting in a high false-positive detection rate (70-80%).

Overvıew of Prostate Cancer Dıagnosıs

In this review, we aim to provide an overview of the current state of MRI/TRUS fusion biopsy, a strategy that is informative and highly useful in the verification of prostate cancer. However, it is also relatively underemphasized in terms of continued exploratory research and innovation and potential clinical use.

The establishment of favorable definitions of these suspicious lesions hinges upon the evolution of data and experience with imaging technology, particularly for MRI, alongside co-registration and interpretation with histological outcome. Subsequently, targeted or selective biopsies can be pursued by tracking the suspicious lesions with the aid of a real-time imaging modality such as the transrectal ultrasound (TRUS) to guide biopsy needles to specific targets.

Non-invasive imaging can detect suspicious lesions in the prostate, either by multiparametric magnetic resonance imaging (MRI) with anatomical and functional imaging, or by positron emission tomography (PET) using radiotracers that target prostate cancer-specific metabolic changes or cell constituents expressed within the space (prostate-specific membrane antigens, PSMA) of the tumor.

Prostate cancer affects a substantial portion of the global population, leading to a high disease burden. Clinical practice currently uses the prostate-specific antigen (PSA) test for diagnosis and subsequent prostate biopsy to verify prostate cancer, but subjects patients who do not have prostate cancer to unnecessary invasive tests. In the last two decades, technological advances in imaging and image-guided biopsies have revolutionized the practice of diagnosing prostate cancer.

Evolutıon and Ratıonale of MRI/TRUS Fusıon Bıopsy

Due to suboptimal performance, multiparametric magnetic resonance imaging (mpMRI) has been introduced as a complementary diagnostic method to replace, or at least to help in selected clinical settings (mainly in patients with native prostate or after radiation therapy), the systematic biopsies, by identifying potential aggressive tumors, with high specificity values. However, the non-guided systematic biopsy still shows limitations in terms of performance, particularly because of the number of unnecessary biopsies and the clinically significant cancers that are missed, problems that can be minimized with additional advanced biopsies that are guided by mpMRI.

The fusion of the images from mpMRI with the ultrasound (US) image provides the ability to appreciate increased signal intensity prior to biopsying, aiming to obtain a targeted biopsy, in a personalized accuracy. This breakthrough technology, introduced in 2006, led to the current evolution of the modern prostate biopsy, called MRI/TRUS fusion targeted biopsy (FUS-TB).

Through much of the last 30 years, the standard diagnostic approach for prostate cancer has been ultrasonography-guided systematic random biopsies of the prostate. There are several factors that restrict the diagnostic accuracy of ultrasonography-guided biopsy, which is the reason why more advanced, enhanced techniques of imaging have drawn significant attention during the last years. As an example, the performance characteristic of trans-rectal ultrasonography (TRUS) in early PCa detection is relatively low, especially for tumors that are located in the lateral side of the prostate. This anatomical limitation is also the reason why the sensitivity of TRUS is highly variable, and ranges from 50% to 95%, depending on the level of experience of the radiologists and the dimension of the tumors and their location. The limited capability in terms of cancer characterization, staging, and monitoring of the disease progression, restraining the use of TRUS in these settings, represents an additional factor that contributes to the overall lower performance of TRUS.

Technıcal Aspects of MRI and TRUS ın Fusıon Bıopsy

In prostate fusion biopsy, after MRI imaging is terminated, the biopsy needle is positioned in the patient’s body under real-time ultrasound viewing and passes through the center of the marker.

A marker is required to allow localization of targets located within the prostate according to MRI images during ultrasound-assisted biopsy. Five hundred core needle biopsy devices (e.g., BiopSocket, Bard Medical) or freehand-mounted US/CT-compatible adhesive markers with a needle (e.g., Visicoil, Cook Medical) can be used as markers for needle biopsies. In the former method, a marker clip is passed through a suction needle, and in the latter method, the adhesive marker is removed from the peel-away sheath using a fine needle.

Ultrasound is an apparatus that allows acquiring images of organs by emitting high-frequency sound, and the reflected echo is captured back. Prostate examination is performed by abdominal (micro-) convex transducers with an average frequency of 3–5 MHz in transrectal and 7–8 MHz in transabdominal methods.

Before discussing recent advances in targeted prostate biopsy, basic knowledge of the two devices required for utilization of this method is required. Magnetic resonance imaging (MRI), first used successfully in the 1980s, allows excellent visualization of soft tissues. Prostate MRI is performed using high-power field magnets. A key concern with MRI is MRI-incompatible materials such as pacemakers, cochlear implants, and metal splinters, which limit its application.

Magnetıc Resonance Imagıng (MRI) ın Prostate Cancer Dıagnosıs

The current prostate cancer diagnostic pathway for biopsy-naïve patients is a transrectal ultrasound-guided (TRUS) prostate biopsy using systematic template biopsies. However, due to its relatively low sensitivity and specificity, there has been an increasing trend in the utilization of traditional multi-parametric magnetic resonance imaging (mpMRI) of the prostate to detect suspicious areas that could harbor significant prostate cancer. These advancements in prostate MRI have led to the creation of novel MRI/TRUS fusion platforms.

In this review, we would like to explore the state of these novel MRI/TRUS fusion platforms in 2015, including their role in the diagnosis of prostate cancer and their impact on biopsy-related endpoints. We have also included an update on individual commercially available MRI/TRUS fusion platforms that appear to be gaining prominence.

Transrectal Ultrasound (TRUS) ın Prostate Cancer Dıagnosıs

Currently, prostate cancer detection needs the acquisition of a tissue sample through the biopsy. In the past, this sample has been taken using a systematic method but during this procedure, clinically significant prostate cancer can be missed. In order to improve prostate cancer detection, in the last years different imaging methods such as MRI or TRUS have been developed. They can improve the guided needle biopsy of the prostate.

Prostate examination should be able to provide valuable kinetic information about the contrast agent to delimitation between prostate cancer and other prostatic pathologies or normal regions. In addition, it should be able to capture detailed morphological indicators that suggest low cancer. From the point of view of the patient, it must not be a very aggressive examination technique and should have a minimum of invasiveness. Then the use of prostate diagnosis techniques (primarily MRI and transrectal prostate ultrasound – TRUS) has been oriented to increase the sensitivity and specificity of the prostate cancer prostate biopsy.

Currently, one of the methods used is fusion technology (MRI/TRUS) for prostate core biopsies. This technique provides real-time visualization and fusion of MRI lesions with 3D ultrasound images. In practice, one should choose a suspicious area from MRI to perform TRUS, and then take the prostate core biopsy with visual guidance. In addition, if the prostate tumor volume is significant, prostate biopsies can be performed by using a prostate shaper, repeating and obtaining a significant tumor sample necessary for additional studies that can indicate the optimal personalized treatment for that patient.

TRUS is an interesting imaging method that can provide some useful structural data of the prostate. Historically, it has been the most used imaging technique in association with prostate biopsy. MRI/TRUS fusion biopsy allows the combination of two of the most performed prostate imagistic methods for prostate core biopsies.

Integratıon and Workflow of MRI/TRUS Fusıon Bıopsy

The fusion of magnetic resonance imaging (MRI) and transrectal ultrasound (TRUS) enables a cognitive and powerful tool to biopsy the prostate in regions of concern rather than biopsy the prostate at random. Multi-parametric MRI findings (PI-RADS v2) have been shown to improve in accordance with the probability of clinically significant carcinoma, and the use of MRI to guide the transrectal acquisition of core biopsy following landmark fastidious optimization results in diagnostic accuracy to rival the current gold standard of the transperineal template technique with MR fusion. The biopsy itself is unchanged, pirate practices of bipedal urologists regarding histologic concern only are reliant on the resultant history, exam and MRI/TRUS fusion data. Correlation of these findings is paramount.

The fusion of MRI and TRUS enables a more personalized approach to prostate biopsy, tailoring the biopsy to each man’s specific imaging and histologic findings. Integration of this new technology into the workflow of our urologic practices, however, requires an understanding of the steps involved and the obstacles that need to be addressed. This narrative aims to provide a comprehensive workflow for MRI/TRUS fusion targeting of the prostate including technical and conceptual nuances that are faced during implementation. A staggered approach is favored such that correct interpretation and translation of PI-RADS v2 and PI-MAP criteria is understood before clinical implementation.

Pre-Bıopsy Preparatıon and Patıent Selectıon

In general, as patient selection, we can determine to decide the men who will benefit from this specific examination for the targeted biopsy to be performed after the positive results in terms of clinically significant prostate cancer data seen in routine urological practice. In cases where some radiological imaging characteristics (lesion location, size, signal intensity, zonal localization, SWE measurements) are interpreted in the imaging, use of additional meta-analyses, findings of the previous biopsy are known to be fairly advantageous.

In prostate MRI reporting and data systems version 2.0, when there is a clinical concern, it is stated that people who do not meet the criteria for active surveillance but need a biopsy are the best candidates for achieving the sensitivity and specificity in the categories of low, intermediate, and clinical presence. Calendared biopsy is still recommended for subjects with a PSA of 50 ng/mL in the imaging and the first requirement of the same level in terms of malign reason (criterion for the recommendation of the biopsy is met as one unknown point and one category 4 point) is ensured.

However, it is aimed to save people from unnecessary biopsies, findings related to the lesion must be given for people who do not need a biopsy in the MRI report and to distribute category 1, 2, and 5 points properly. The overall sensitivity and specificity of the mpMRI are 57–87% and 53–90%, respectively, but the requirement for subsequent transrectal biopsy at the first request can be increased up to 92% by combining the imaging characteristics with the PSA level and the values, the personal and specific choices of the patient, other comorbid conditions, and that have developed already and the cumulative long-term side-effects should cease.

Before biopsy planning and patient selection, one of the most critical areas of MRI/TRUS fusion biopsy should be covered in detail. Although the procedure of fusion biopsy and professionalism of the team is extremely important for worthy outcomes, preparation of the patient and data to be sent to the radiologist to make the most precise and sensitive interpretation is also very important on the way to recognize patients to be biopsied by using fusion biopsy software. Although the use of the 3-tesla magnetic field is superior in terms of identifying and grading the tumor, the urinary and non-urinary artifacts were seen more in priori but more precisely with T2W assessment of the 3-tesla device in the literature. Diffusion-weighted MR imaging with higher b-values (b = 1600–2000), preferably an endorectal coil, and dynamic contrast-enhanced examinations including postprocessing corrections have increased the specificity and positive predictive value of mpMRI in order to get higher diagnostic precision.

Image Fusıon and Targeted Bıopsy Procedures

To perform fusion biopsy, a pelvic MRI is typically performed, both with and without contrast. The images are taken in the axial, sagittal, and coronal planes. The images are then acquired into a urology fusion system, where the MRI map and the corresponding ultrasound images are co-registered and ready to use for the targeted biopsy. With the biopsy device longitudinally captured in the transrectal probe, the mapping and registration process must happen in less than 5-10 s in order to keep the registration (and 3D target) displayed in the ultrasound. If it takes much longer than this, the patient must be re-registered and the image re-acquired to ensure correct targeting. These events can be challenging during prostate capsule deformation or significant movement of the prostate gland.

In image fusion prostate biopsy, a pre-biopsy MRI is performed and used as a map for selecting potential biopsy targets. During MRI/TRUS fusion biopsy, the urologist can visualize 3D targets captured in the MRI on their ultrasound monitor in real time. These 3D targets are overlaid on the 2D plane of the ultrasound. Because a transrectal probe is used, the majority of the field of view during an ultrasound is apical to basal (inferior to superior). Nonetheless, in each clip in which the biopsy device is visible, the MRI volume will display. This capability ensures good overlap between biopsy targets in an MRI and the ultrasound image. The urologist uses this map to direct their biopsy needle. With MRI/TRUS fusion biopsy, the urologist can direct their biopsy needle to exact locations in the prostate. Post-biopsy, the biopsied cores and their respective targets are overlaid on the MRI, and the results are compared with the initial imaging information.

Clınıcal Utılıty and Effıcacy of MRI/TRUS Fusıon Bıopsy

Several models and scoring systems have been created to utilize in assessing the likelihood of significant disease and discriminate benign findings. One such scoring system, the centrally reviewed Prostate Imaging Reporting and System (PI-RADS), had interobserver agreement and a high level of accuracy in imaging that Portalez et al. reported in equivocal or indeterminate lesions by MRI. PI-RADS was able to predict aggressive PCa using the clinical cutoff of >4 with an NPV of 96% with sensitivity and specificity of 100% and 57%, respectively.

A scoring system developed and validated by Radtke et al., the European Society of Urogenital Radiology (ESUR) scoring system, had a high negative predictive value (NPV) as a systematic approach to mapping cancer with a sensitivity and specificity of 63.2% and 81.3%, respectively. Their data support the concept that ESUR scoring helps to reduce missed cases which one might avoid with MRI/TRUS fusion biopsy. Men were able to be re-classified to a lower risk group, avoiding mortality due to over-treatment. These findings are consistent with Gaur et al.’s findings that, in localized PCa, utilizing mpMRI can act as a biomarker to assess the disease progression at follow-up.

Furthermore, recognizing MRI as a soft tissue tumor biomarker, in addition to NI-RADS, Rouviere et al. developed a patient-based nomogram that utilized patient data, MRI data, and biopsy data to predict overall adverse pathology and reduce the number of low-grade cancers. Thus, as smartphone app developers and investigators look to expedite the training programs related to understanding MRI for lesion inception and characterization, telemedicine services might be employed to achieve worldwide dissemination of the technology for a model that works best for both patients and physicians.

In a cohort of 1,003 men who underwent both MP-MRI and MRI/TRUS fusion biopsy, Bjurlin et al. reported a higher cancer detection rate (59% vs. 73%) and higher positive predictive value (23% vs. 33%) of MRI-detected lesions requiring MRI/TRUS fusion biopsy compared to their prior study that included all comers. Application of a negative MRI/TRUS fusion biopsy encouraged a lower likelihood of secondary prostate biopsy compared to systematic cores. Combination use of PSA, MRI radiology grade, and MR-directed biopsy allowed for greater confidence in deciding which patients could avoid subsequent systematic biopsy without compromising PCa detection. In the biggest study to date, Puech et al. evaluated the incidence of MRI/US lesion and how that related to overall PCa detection. They found that MRI/US guided targeted biopsies were performed with greater frequency in patients with a suspicious area on MRI but demonstrated this finding was not independent of PSA or age.

Dıagnostıc Accuracy and Prognostıc Value

The technological innovation that is known as MRI/TRUS fusion, a fusion of ultrasound and MRI imaging, solves several issues. By utilizing the combination of each of the imaging technologies, including software that combines the MRI and live, bi-planar transrectal ultrasound (TRUS), the emergence of the MRI/TRUS fusion biopsy system is ushering in an entirely new level of precision prostate cancer diagnosis. As a direct result, more precise prostate biopsy procedures are now typically being utilized by Sloan Kettering facilities and other top-tier healthcare facilities, providing instantaneous visual assistance and biopsy needle guidance.

The traditional random biopsy of the prostate uses ultrasound imaging alone, which is limited in its ability to identify clinically significant prostate cancer. However, with the combined power of live ultrasound and superimposed MRI imaging of the prostate, treatment of the prostate due to suspected prostate cancer by targeted biopsies is much improved. The use of the real-time, MRI/TRUS fusion biopsy devices is transforming traditional prostate care, revolutionizing the way prostate cancer is diagnosed and treated.

It allows urologists an enormous improvement in targeted detection, localization of, and guidance for biopsies. Offering a much higher level of observational information, the MRI scan is now being utilized by an increasing number of urologists to precisely and directly target areas requiring biopsy, thus reducing the risks of more random biopsy sampling. Complication rates of 5-8%, including bleeding, pain, and infection, continue to be a problem where core needle biopsies are taken randomly from the more commonly used prostate treatment imaging method.

Comparıson wıth Conventıonal Bıopsy Technıques

Few technical advancements provided by 3T multiparametric TRUS/MRI fusion have been integrated into modern clinical practice. While MRI is still frequently praised for its capability to target biopsies to concerning areas, few studies review the combined biopsy techniques within a more selective cohort, and direct comparisons to our knowledge have not been performed. T2 axial imaging seems to be sufficient to guide biopsies in multiple reports, with only a single case outlined that used the additional information of dynamic contrast-enhancement series.

The cost of repeat biopsies, both to the patient and the healthcare provider, and the difficulty in consistent sampling across regions of interest, reduce the effectiveness of conventional transrectal ultrasound-guided biopsy. In a recent report analyzing over 2,500 men undergoing MRI followed by biopsy over a six-year period, multiparametric MRI with the use of sophisticated reporting systems has been observed to decrease negative biopsies and increase detection of high-grade cancers in biopsy-naïve patients. Furthermore, 3D manipulation of MRI data can offer insight to the urologist on the precise location within the prostate that might allow for advanced guidance during biopsy.

Future Dırectıons and Emergıng Technologıes ın Prostate Cancer Dıagnosıs

A major controversial question will be which GPS technology with which type of needle driver may be best for the MRI/TRUS fusion biopsy? The combination of GPS needle driver (A and B type), Logic 9 and fusion biopsy protocol may provide a more precise biopsy of the prostate than the original hell or cancer GPS system.

This technology represents another step in the continued evolution of the prostate biopsy process. In the future, other similar promising GPS needle driver systems will be developed with time for the accurate and diagnostic fusion biopsy of the prostate. With further advances, the biological characterization of the MRI-identified lesions may become pathognomonic. Interference will be minimized, and the efficacy, accuracy, and safety of prostate biopsy will be maximized.

Facilities evaluating MRI/TRUS fusion biopsy technology should be well-prepared. This paper, with a companion paper, provides the background knowledge essential for the urologist to implement quality prostate fusion biopsy. However, before embarking on prostate biopsy, one must first own a quality prostate device with the appropriate hardware and software, including an MRI-TRUS fusion system and a compatible computer.

Artıfıcıal Intellıgence and Machıne Learnıng Applıcatıons

Beyond AI modeling, registrational clinical trial data have lagged in the prostate cancer space, and mathematical modeling to predict outcomes for different procedural options is a fertile area for AI investigation. This is exemplified in the knowledge gaps associated with active surveillance for prostate cancer. Diffusion of these advanced clinical decision support tools will be further enabled by additional vendor innovations such as universal viewing platforms available for clinical diagnostics, pathology radiology, anesthesia, and robotic interventions.

Also required is the availability of regulatory-approved advanced clinical decision support tools both to study their utility and for access by other developers in order to build upon them. Additionally, to reduce overdiagnosis and overtreatment and allow for low-cost, non-invasive longitudinal monitoring of the patient’s cancer burden, wider availability of highly accurate liquid biopsies and tissue autonomous multianalyte assays utilizing radiomics will further benefit capital, digitalization, data analytics, diagnostics, and genomics in the urologic disease market.

The field of prostate cancer diagnosis has benefitted greatly from the interest and advancements made in the field of artificial intelligence and machine learning. Initially, a large dataset was required to fine-tune discrimination thresholds and modify and calibrate the sampling process for prostate MRI to improve accuracy and reduce sampling error.

In larger part as a result of the heavy involvement in industry, the process is now more automated, and the increased availability of prostate MRI and more standardized hyperparametric MRI sequences have created larger, more efficient data sets. This, in turn, has increased manufacturability and health system ease of adoption. High levels of accuracy in identifying and locating the index lesion are now possible. By engaging machine learning specialists, disease-specific artificial intelligence, predictive tools, and decision support tools can be developed. Prostate cancer grading on the MRI is currently an area of more widespread clinical development. Deep learning neuro-registration of MRI fiducial and prostate centre of mass alignment tools for MRI/TRUS fusion are also available.

Enhancements ın Imagıng Modalıtıes

Magnetic resonance imaging (MRI) of the pelvis is utilized to survey individuals with raised prostate-specific antigen levels, negative harsh computerized rectal assessment, and first leukemia prognosis biopsy, and when there is doubt on the degree of illness and whether the illness is organ-bound. The diagnostically extended imaging methodology is the improvement of raw transrectal or even pubic ultrasound to the location target of biopsy with actual-time ultrasound/MRI picture enrollment utilized in both cognitive/visual combination or sophisticated ultrasound/MRI combination strategy.

MRI has expanded the sensitivity from 48 to 93% when the standard transrectal ultrasound-guided biopsy identified a lower Golf GPS stage prostate volume growths. However, the disadvantage of MRI-directed biopsy is the cost, boundaries from the MRI models, machine understanding required by the creators, and being generally carried out with MRI/TRUS manual combination.

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