EURURO Vol. 71 No. 4

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Importantly, a large randomised controlled trial comparing
all three techniques of MRI-GB is underway .
3.7.2. Strengths and limitations
The number of studies investigating MRI-GB was quite
large, but there was considerable heterogeneity in the
applied methodology. The majority of studies report on
subsequent cohorts of patients undergoing target biopsy
procedures. The number of studies that applied a compara-
tive test (such as TRUS-GB) in conjunction with target
biopsy is limited. And finally, the quality of MRI acquisition
seems to demonstrate significant heterogeneity, directly
influencing the outcome of MRI-GB.
The major strength of this meta-analysis is that all
included studies have used MRI acquisition protocols in
accordance to the latest imaging guidelines, hereby safe-
guarding some level of homogeneity in the selection
procedure for subsequent MRI-GB. Furthermore, only
studies performing both MRI-GB and TRUS-GB within the
same population were included in the meta-analysis. As a
consequence the number of eligible studies was limited,
especially for MRI-TB where lack of simultaneous TRUS-GB
seems to be most common.
The heterogeneous usage of definitions for csPCa
incorporating PSA (density), clinical stage, and histology
among the different series is a major concern for this
current meta-analysis and even more so because most
definitions have their origin in the systematic biopsy
setting. As such they are, at least partially, based on
variables such as cancer core length, and number of positive
cores and therefore might significantly overestimate the
number of detected csPCa in a targeted biopsy setting.
Consequently commonly used definitions such as the
Epstein criteria seem to become outdated, whereas new
generally accepted criteria have yet to be formulated for
MRI-GB. Of the 14 studies used for the analysis on csPCa in
this systematic review, only three used a definition of csPCa
solely based on the presence of a Gleason 4 component on
biopsy
Furthermore, the method of MRI evaluation and the
applied threshold for MRI-GB seems to demonstrate
heterogeneity. This will directly impact tumour detection
yields, as studies that incorporate patients with benign
findings on MRI will demonstrate lower tumour yields
than studies that only incorporate patients with very
suspicious findings on MRI. Potentially the PIRADS grading
system can solve this problem, but it was only introduced
several years ago. Therefore, to date, the number of studies
using this grading system is limited. Thirdly, we found
significant variation concerning biopsy conduct, especially
concerning comparative testing. Not only did the number of
cores on TRUS-GB vary, but also whether systematic biopsy
was performed prior to or following MRI-GB. Moreover
several techniques of FUS-TB are commercially available,
and this variation can impact accuracy of targeting. Rigid
image fusion (where the MRI prostate contour is projected
over the TRUS image, and used to match landmarks during
the planning phase of biopsy) is likely to be less accurate
when compared to elastic image fusion (where the prostate
is contoured on both the MRI and the TRUS image, and the
contours are fused correcting for prostate deformation and
movement during the entire biopsy procedure) . Finally,
the absence of lesion specific descriptive characteristics,
such as size, in the majority of studies limits the ability to
perform accurate comparison of the various MRI-GB
techniques. If only larger lesions are biopsied, this may
negatively affect the potential of MRI-TB.
A cursory repeat search on December 15, 2015 identified
another four major relevant publications All
studies performed MRI-GB in conjunction with TRUS-GB.
Three studies used FUS-TB, and one paper used MRI-TB to
performMRI-GB in patients at risk for PCa. The three studies
using FUS-TB concluded that MRI-GB detects more csPCa
compared with TRUS-GB while decreasing the detection of
clinically insignificant PCa . Although one paper
did conclude that omitting TRUS-GB would miss some
clinically significant cancers . The fourth paper per-
formed MRI-TB in conjunction with TRUS-GB in biopsy
naı¨ve patients. The authors concluded that MRI-GB and
TRUS-GB have equivalent high detection yields, although
MRI-GB required significantly less biopsy cores compared
with TRUS-GB to accomplish this diagnostic yield
. These results are in accordance with the findings
of this current meta-analysis, and are summarised in
Appendix 2.
4. Conclusions
In men at risk for PCa who have tumour suspicious lesions
on MRI, subsequent MRI-GB of these lesions demonstrates
similar overall tumour detection rates compared with
systematic TRUS-GB, although the incidence of PCa is
increased in targeted cores when compared with systematic
cores. Moreover, the sensitivity of MRI-GB is increased for
the detection of csPCa, and decreased for clinically
insignificant PCa when compared with TRUS-GB.
Based on the studies included in this meta-analysis MRI-
TB demonstrates a superior performance in overall PCa
detection when compared with COG-TB. For overall PCa
detection and detection of csPCa, FUS-TB has a similar
performance compared with MRI-TB. The current number
of randomised controlled trials performing a head-to-head
comparison of the various techniques for MRI-GB is limited
and comparative analysis is restricted by the absence of
data on lesion characteristics.
Author contributions: Olivier Wegelin had full access to all the data in the
study and takes responsibility for the integrity of the data and the
accuracy of the data analysis.
Study concept and design: Wegelin, van Melick, Somford, Barentsz, Bosch.
Acquisition of data: Wegelin.
Analysis and interpretation of data: Wegelin, van Melick, Somford, Hooft,
Reitsma, Barentsz, Bosch.
Drafting of the manuscript: Wegelin, van Melick, Somford, Hooft, Reitsma,
Barentsz, Bosch.
Critical revision of the manuscript for important intellectual content:
Wegelin, van Melick, Somford, Hooft, Reitsma, Barentsz, Bosch.
Statistical analysis: Wegelin, Reitsma, Hooft.
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