








































This is an open access article under the terms of a license that permits non-commercial use, provided the original work is properly cited.  
© 2023 The Authors. Société Internationale d'Urologie Journal, published by the Société Internationale d'Urologie, Canada.

Key Words Competing Interests Article Information

Targeted biopsy, prostate cancer, 
multiparametric MRI, fusion biopsy

None declared. Received on October 15, 2022 
Accepted on October 22, 2022 
This article has been peer reviewed.

Soc Int Urol J. 2023;4(2):139–141

DOI: 10.48083/RIXC8512

MRI to Ultrasound Cognitive Targeted Prostate 
Biopsy Provides All the Benefit of Ultrasound  
Fusion Without the Increased Resources

Jonathan Suderman,1 Miles Mannas1,2

1 Department of Urologic Sciences, University of British Columbia, Vancouver, Canada 2 Vancouver Prostate Centre, Vancouver, Canada

A Diagnostic Dilemma

In 2013, the American Urological Association (AUA) set out to maximize the clinical utility of the diagnostic prostate 
biopsy[1]. Goals included maximizing detection of clinically significant prostate cancer (csPCa), minimizing over-
detection of clinically insignificant prostate cancer (ciPCa), and decreasing cost to the patient and the system. 
Historically, systematic template biopsies resulted in over-detection and overtreatment of ciPCa. The goal of prostate 
biopsy has shifted from merely identifying prostate cancer towards diagnosing only csPCa. Use of MRI to risk-
stratify patients before biopsy and targeting regions of interest identified on MRI increases detection of csPCa, while 
minimizing detection of ciPCa[2]. MRI targeted biopsies have been developed in 3 different modalities: cognitive 
targeted biopsy (COG-TB), MRI to ultrasound fusion targeted biopsy (FUS-TB) and in-bore. The most common 
modalities are FUS-TB and COG-TB. Despite multiple studies attempting to answer this question, debate remains 
over which method yields superior results.

FUS-TB is expensive, time-consuming, and resource-limited, and has not been definitively shown to improve diag-
nostic accuracy over COG-TB. Arguments for FUS-TB include a shorter operator learning curve, and a trend toward 
improved detection of csPCa. There is no or low-quality evidence supporting these claims. FUS-TB creates a signifi-
cant burden on the health care system, while COG-TB is a simple and low-cost procedure. This commentary presents 
an argument for COG-TB to remain standard of care when completing diagnostic prostate biopsy.

A Brief Literature Summary
In the seminal PROFUS trial by Wysock et al., cancer detection rates of FUS-TB were compared with COG-TB. Men 
with suspicious lesions on MRI (n = 125) underwent transrectal FUS-TB, then had 2 COG-TB cores collected with 
standard template 12-core biopsy. Detection of cancer and csPCa was not significantly different between FUS-TB and 
COG-TB (32.0% and 20.3%; 26.7% and 15.1%, respectively)[3]. FUS-TB did show increased detection of csPCa in the 
anterior transition zone and in small lesions detected on MRI. The study was not powered to detect differences in 
tumor location or size; therefore, interpretation of results must be made with caution.

In 2019, the SmartTarget Biopsy Trial assessed concordance between COG-TB and FUS-TB. Patients with a discrete 
lesion of PI-RADS 3-5 were enrolled, and 129 patients had both biopsies performed. Each modality detected 86% of 
csPCa[4]. Notably, each missed 14% of csPCa that was detected by the alternate modality.

In 2020, a systematic review and meta-analysis by Watts et al. identified 9 studies (N = 1714) undergoing MRI 
targeted biopsy[5]. Studies included transperineal and transrectal biopsies, although findings were unchanged when 
transperineal biopsies were removed from the analysis. They did not find a statistically significant difference in odds 

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ratios for overall and csPCa detection (OR 1.11, 95% CI 
0.91 to 1.36, P = 0.30 and OR 1.13, 95% CI 0.89 to 1.44, 
P = 0.32, respectively)[5]. The authors of this meta-anal-
ysis were unable to stratify their data based on user expe-
rience and did not assess the detection of ciPCa.

In a recent study by Izadpanahi et al., FUS-TB was 
compared with COG-TB in a randomized controlled 
trial (n = 199)[6]. This trial showed a significantly higher 
detection of overall and csPCa for FUS-TB (44.4% and 
33.3%, respectively) compared with COG-TB (31.0% 
and 19.0%, respectively)[6]. However, a higher detection 
rate of BPH was reported in the COG-TB versus the 
FUS-TB group (66.0% versus 47.5%). No subsequent 
analysis was completed on prostate size despite a known 
inverse correlation between size and cancer detection[7]. 
This critical methodological flaw again limits interpreta-
tion and generalizability of the results.

Putting the Numbers into Context
No strong evidence exists suggesting FUS-TB is 
superior to COG-TB. COG-TB is simple and cost-
effective, whereas FUS-TB is cumbersome and costly. 
Operation of FUS-TB requires significant infrastructure 
including equipment maintenance, image acquisition/
segmentation, data processing, and device operation.

The PROFUS study suggests distinct situations (ante-
rior transition zone and smaller lesions) in which 
FUS-TB may be beneficial. However, this study was not 
powered to make such conclusions. Regarding size, 
targeting accuracy for FUS-TB has been studied, claim-
ing accuracy for lesions ≥ 3 mm. The authors recognize 
that the study’s ex vivo prostate models do not fully 
represent critical in vivo conditions, given the model’s 
sharper image contours, and the lack of tissue movement 
and deformation seen during in vivo biopsy[8]. Further, 
prostate cancer may exist within 10 mm of a lesion 
detected on MRI, allowing a larger target for small radio-

graphic lesions for FUS-TB and COG-TB alike[9]. Press 
et al. showed that targeting hypoechoic regions in close 
proximity to an MRI identified region of interest inde-
pendently predicts detection of csPCa[10]. Hypoechoic 
regions can be identified and directly applied to the 
COG-TB technique, improving biopsy success rates. 
With a mean target size of 12 mm (IQR 8 to 15mm)[2], 
75% of lesions are greater than or equal to 8 mm.  
This suggests FUS-TB might provide benefit for only a 
minority of cases, and certainly should not be widely 
adopted as standard of care for all MRI identified  
prostate lesions.

The SmartTarget Biopsy Trial showed both modalities 
missed an equal number of csPCa[4]. The meta-analysis 
by Watts et al. showed no significant difference between 
the 2 modalities, and no conclusions can be drawn about 
the benefits of a faster learning curve for FUS-TB[5]. 
One study does compare operator learning curves 
between FUS-TB and COG-TB. The authors show that 
an experience plateau is reached more quickly with 
FUS-TB than with COG-TB[11]. However, only 3 opera-
tors were compared in a retrospective manner, introduc-
ing selection bias. Further, transrectal approach was used 
for all COG-TB, whereas transperineal was used in 55% 
of FUS-TB, introducing significant heterogeneity into 
the sample, risking confounding the results. Finally, the 
randomized controlled trial by Izadpanahi et al. shows a 
difference between FUS-TB and COG-TB. This study is 
significantly limited by its discrepant BPH findings and 
lack of prostate size reporting, despite a known inverse 
correlation between prostate size and cancer detection 
rates[6].

Returning to the AUA’s 2013 mandate, data suggest 
that FUS-TB does not maximize detection of csPCa, 
minimize over-detection of ciPCa, or decrease cost to the 
patient and the system. Therefore, COG-TB should 
remain the standard of care for targeted diagnostic pros-
tate biopsy until clear evidence suggests otherwise.

140 SIUJ  •  Volume 4, Number 2  •  March 2023 SIUJ.ORG

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References

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141SIUJ.ORG SIUJ  •  Volume 4, Number 2  •  March 2023

MRI to Ultrasound Cognitive Targeted Prostate Biopsy Provides All the Benefit of Ultrasound Fusion Without the Increased Resources

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