EURURO Vol. 72 No. 2

178 320

1. Introduction
Prostate cancer (PCa) is the second leading cause of cancer-
related mortality in Western men . With the recent
technological advancements and growing availability,
multiparametric magnetic resonance imaging (mpMRI)
currently is increasingly being used for guiding several
aspects of PCa management, including detection, staging,
and treatment planning . Despite abundant evidence in
the literature reporting high accuracy of mpMRI for PCa
diagnosis, widespread acceptance has been hampered by
several factors including difficulty of interpretation, lack of
standardized criteria for interpretation (ie, use of Likert
scales based on the radiologist’s subjective level of
suspicion for PCa), and resulting substantial inter-reader
variability .
To bring standardization to the evaluation and
reporting of mpMRI of the prostate, the European Society
of Urogenital Radiology (ESUR) published a guideline
termed Prostate Imaging Reporting and Data System (PI-
RADS) in 2012 . PI-RADS was generated based on
expert consensus and provides a detailed scoring system
for each MRI sequence (T2-weighted imaging [T2WI],
diffusion-weighted imaging [DWI], dynamic contrast-
enhanced MRI [DCE-MRI], and MR spectroscopy) for the
presence of clinically significant PCa (csPCa). Several
investigators have validated the accuracy and reproduc-
ibility of PI-RADS, and a recent meta-analysis reported
pooled sensitivity and specificity of 0.78 and 0.79,
respectively . However, as there was no guideline for
the generation of an overall score, different research
groups utilized various measures for this purpose—some
used a sum of the scores from each sequence (ranging
from 3 to 15), whereas others used an overall score of 1–5
Furthermore, emerging data questioned the value of
curve-type analysis of DCE-MRI In addition, investi-
gators suggested that some sequences may be more
important in determining the likelihood of PCa (ie, DWI in
the peripheral zone [PZ] and T2WI in the transition
zone [TZ]) rather than equal weighting for all sequences
.
To address these issues, the ESUR and American College
of Radiology recently released the updated PI-RADS version
2 (PI-RADSv2) . The main changes fromPI-RADSv1 to PI-
RADSv2 are the following: (1) introduction of dominant
sequences according to zonal anatomy (DWI for the PZ and
T2WI for the TZ), (2) limited contribution of DCE-MRI data
as merely presence and absence of early focal enhancement,
and (3) generation of an overall score (1–5) integrating
findings across all MRI sequences.
Since then, several studies assessing the value of PI-
RADSv2 have been published. However, the diagnostic
performance of this new scoring system has not been
evaluated systematically. Therefore, the purpose of our
study was to assess the diagnostic performance of PI-
RADSv2 for the detection of PCa. In addition, we aimed
to compare the diagnostic performance of PI-RADSv1
and PI-RADSv2 in studies available for head-to-head
comparison.
2. Evidence acquisition
This meta-analysis was performed and written according to
the preferred reporting items for systematic reviews and
meta-analyses (PRISMA) guidelines .
2.1. Literature search
A computerized search of MEDLINE and EMBASE up to
December 7, 2016, was performed in order to identify
studies evaluating the diagnostic performance of PI-RADSv2
for the detection of PCa. The search query combined
synonyms for PCa, MRI, and PI-RADS as follows: (prostate
cancer OR prostatic cancer OR prostate neoplasm OR
prostatic neoplasm OR prostate tumor OR prostatic tumor
OR prostate carcinoma OR prostatic carcinoma OR PCa) AND
(magnetic resonance imaging OR MRI OR MR) AND
(prostate imaging reporting and data system OR pi-rads
OR pi rads OR pirads). Bibliographies of identified articles
were also screened to expand the scope of search. Our
search was limited to publications in English.
2.2. Study selection
2.2.1. Inclusion criteria
Studies were included if they satisfied all the following
requirements according to the PICOS criteria : (1)
included patients with suspected or diagnosed PCa; (2) for
index test, mpMRI of the prostate including all required
sequences of T2WI, DWI, and DCE-MRI was performed and
assessed with a PI-RADSv2 scoring system; (3) for
comparison, a reference standard based on the histopatho-
logical examination of radical prostatectomy or biopsy was
used; (4) results were reported in sufficient detail for the
reconstruction of 2 2 tables and determination of
sensitivity and specificity at specified cutoff values for
evaluating the diagnostic performance of PI-RADSv2; and
(5) studies had to be original articles.
2.2.2. Exclusion criteria
Studies were excluded if any of the following criteria were
met: (1) studies involving <10 patients; (2) review articles,
guidelines, consensus statements, letters, editorials, and
conference abstracts; (3) studies using only PI-RADSv1 for
the evaluation of mpMRI of the prostate; (4) studies focusing
on topics other than using the PI-RADSv2 system for
diagnosing PCa (ie, staging and prediction of biochemical
recurrence); and (5) studies with overlapping patient
population.
Two reviewers (S.W. and C.H.S., with 3 yr of experience in
performing systematic reviews and meta-analyses) inde-
pendently evaluated the eligibility of the selected studies
from the literature. Disagreements, if present between the
two reviewers, were resolved by consensus via discussion
with a third reviewer (S.Y.K.).
2.3. Data extraction and quality assessment
We extracted the following data regarding study design and
results from the selected studies using a standardized form:
E U R O P E A N U R O L O G Y 7 2 ( 2 0 1 7 ) 1 7 7 – 1 8 8 178