Elsevier

European Urology Focus

Volume 7, Issue 5, September 2021, Pages 1019-1026
European Urology Focus

Prostate Cancer
Diagnostic Accuracy of Microultrasound in Patients with a Suspicion of Prostate Cancer at Magnetic Resonance Imaging: A Single-institutional Prospective Study

https://doi.org/10.1016/j.euf.2020.09.013Get rights and content

Abstract

Background

Multiparametric magnetic resonance imaging (MRI) represents the gold standard for the diagnosis of clinically significant prostate cancer (csPCa). The search for alternative diagnostic techniques is still ongoing.

Objective

To determine the accuracy of microultrasound (microUS) for the diagnosis of csPCa within prospectively collected cohort of patients with a suspicion of prostate cancer (PCa) according to MRI.

Design, setting, and participants

A total of 320 consecutive patients with at least one Prostate Imaging Reporting and Data System (PIRADS) ≥3 lesion according to MRI were prospectively enrolled.

Intervention

All patients received microUS before prostate biopsy using the ExactVu system; the Prostate Risk Identification using microUS (PRI-MUS) protocol was used to identify targets. The urologists were blinded to MRI results until after the microUS targeting was completed. All patients received both targeted (based on either microUS or MRI findings) and randomized biopsies.

Outcome measurements and statistical analysis

The sensitivity and specificity of microUS to determine the presence of csPCa (defined as at least one core with a Gleason score ≥7 PCa) were determined. Multivariable logistic regression analysis was fitted to determine the predictors of csPCa.

Results and limitations

Clinically significant PCa was diagnosed in 116 (36.3%) patients. The sensitivity and negative predictive value of microUS for csPCa diagnosis were 89.7% and 81.5%, while specificity and positive predictive value were 26.0% and 40.8%, respectively. A combination of microUS-targeted and randomized biopsies would allow diagnosing the same proportion of csPCa as that diagnosed by an approach combining MRI-targeted and randomized biopsies (n = 113; 97.4%), with only three (2.6%) csPCa cases diagnosed by a microUS-targeted and three (2.6%) by an MRI-targeted approach. In a logistic regression model, an increasing PRI-MUS score was an independent predictor of csPCa (p ≤ 0.005). The main limitation of the current study is represented by the fact that all patients had suspicious MRI.

Conclusions

Microultrasound is a promising imaging modality for targeted prostate biopsies. Our results suggest that a microUS-based biopsy strategy may be capable of diagnosing the great majority of cancers, while missing only few patients with csPCa.

Patient summary

According to our results, microultrasound (microUS) may represent an effective diagnostic alternative to magnetic resonance imaging for the diagnosis of clinically significant prostate cancer, providing high sensitivity and a high negative predictive value. Further randomized studies are needed to confirm the potential role of microUS in the diagnostic pathway of patients with a suspicion of prostate cancer.

Introduction

Prostate cancer (PCa) is the most frequently diagnosed cancer among men and the third leading cause of cancer-related mortality [1], [2]. The traditional diagnostic workup of patients suspected for PCa involved prostate-specific antigen (PSA) screening along with transrectal ultrasound (TRUS)-guided biopsy, where 10–12 cores are systematically taken per patient [3]. Unfortunately, this diagnostic pathway is insufficient due to its low sensitivity and specificity, resulting in both overdiagnosis of clinically insignificant PCa and underdiagnosis of clinically significant PCa (csPCa), with at least 28% of patients with an elevated PSA level who have had an initial negative biopsy and who are diagnosed with PCa in a following repeat biopsy [4].

As conventional gray-scale TRUS is not considered by current guidelines as a reliable tool to detect PCa, several imaging techniques enabling targeted biopsies of areas suspicious for malignancy have been investigated [5]. Among these, multiparametric magnetic resonance imaging (MRI) has emerged as an effective tool for the detection of csPCa [6], [7], [8], [9]. Several prospective randomized studies have been reported providing high-level evidence supporting the adoption of an MRI-targeted approach both in the initial and in the repeat biopsy setting [10], [11], [12]. As a consequence, current guidelines recommend the use of MRI-targeted biopsies in these settings [5]. However, the consistent number of csPCa missed by the MRI-targeted biopsy approach still contraindicates the omission of systematic prostate biopsies [8], [13]. In addition, the widespread adoption of MRI has been limited by its availability, increased costs, requirement for radiological expertise, and the complexity related to the MRI-targeted biopsies procedure [14], [15].

Microultrasound (microUS) is a new imaging modality that operates at high frequency (29 MHz), with the resulting microUS images having a resolution of up to 70 μm [16]. Microultrasound uses the Prostate Risk Identification using microUS (PRI-MUS) protocol to characterize and target suspicious regions for PCa, similar to the Prostate Imaging Reporting and Data System (PIRADS) protocol for MRI [17]. The microUS procedure is nearly identical to the standard conventional TRUS, with the additional benefit of enhanced imaging resolution and visualization of suspicious tissue that enables real-time targeted biopsies. The learning curve for microUS for operators already performing TRUS is expected to be short and is limited to simple technique issues and understanding of PRI-MUS characteristics [17]. The aims of the current study were to evaluate the effectiveness of microUS-guided biopsy in the detection of csPCa, defined as a Gleason score of ≥7, and to compare the diagnostic performance of MRI and microUS.

Section snippets

Study population

The study population consisted of 320 consecutive men who were prospectively enrolled at our institution between October 2017 and September 2019. All patients were referred to our center for a suspicion of PCa based on elevated PSA values or abnormal digital rectal examination, and presented with at least one PIRADS ≥ 3 lesion (defined according to the PIRADSv2 protocol) after undergoing prostate multiparametric MRI (mpMRI; performed either with a 1.5-T scanner with an endorectal coil or with a

Study demographics

Table 1 shows patients’ characteristics and stratification according to biopsy setting. The majority of patients had a maximum PIRADS lesion score of 4 (65.3%). Microultrasound identified lesions in 265/320 (79.7%) patients, with the majority having a maximum PRI-MUS score of 4 (49.7%). Significant differences were observed in total PSA, prostate volume, number of biopsy cores taken, and number of positive biopsy cores between patients undergoing first or repeated biopsy. Of the 255 patients

Discussion

In the current prospective study, we evaluated the role of microUS in the detection of csPCa. Our findings showed a similar improvement in csPCa detection by adding microUS targets to that by adding MRI targets. Furthermore, these two modalities appear to provide complementary information that could easily be combined into a single procedure in order to maximize the detection of csPCa.

The role of conventional TRUS in the diagnosis of PCa, at least when only the b-mode imaging is considered, is

Conclusions

Microultrasound demonstrated a considerable potential as a targeted biopsy modality, providing high sensitivity and an acceptable NPV for csPCa. In consequence, microUS may improve the detection rate of csPCa compared with systematic randomized biopsies. In addition, microUS and MRI may be used as complementary imaging techniques, as they appear to provide independent information in a non-negligible proportion of patients.


Author contributions: Giovanni Lughezzani had full access to all the data

References (28)

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