EURURO Vol. 72 No. 6

E166 1030

Letter to the Editor
Reply to Jae Heon Kim, Bora Lee, and Benjamin I.
Chung’s Letter to the Editor re: Sungmin Woo,
Chong Hyun Suh, Sang Youn Kim, Jeong Yeon Cho,
Seung Hyup Kim. Diagnostic Performance of
Magnetic Resonance Imaging for the Detection
of Bone Metastasis in Prostate Cancer:
A Systematic Review and Meta-analysis. Eur Urol.
In press.
We thank Kim et al for showing interest in our systematic
review and meta-analysis Several of the concerns raised
in their letter are important regarding the application of our
results.
First, our results should be interpreted with caution, as
the studies included were not free of bias. As Kim et al
mention, most were retrospective observational studies and
the reference standard was ‘‘best value comparator’’, which
cannot be considered robust for determining bone metas-
tasis, therefore rendering potential for bias. Although our
study question was not to ‘‘compare’’ the performance of
magnetic resonance imaging (MRI) and bone scintigraphy,
had there been randomized controlled trials comparing the
two modalities, we could have included them in our meta-
analysis and provided more firm conclusions. Furthermore,
since comparison between the two modalities was not the
purpose of our meta-analysis, we did not consider using
statistical methods such as conditional sensitivity and
specificity.
Second, clarification regarding interpretation of MRI and
the reference standard was requested. (1) The interval
between MRI and the reference standard was not reported
in most studies. This could be a limitation, as a very long
interval may result in bone metastasis that was not present
when performing MRI (ie, false negative). (2) The radi-
ologists’ interpretation of MRI was blinded to clinicopatho-
logical information, as described in our meta-analysis. (3)
The best value comparator included MRI in some of the
studies included, meaning that derivation of the reference
standard was not always blinded to the index test.
Third, the patients included were heterogeneous, com-
prising both newly diagnosed and previously treated
prostate cancer patients. Owing to significant clinical
differences, pooling results from both populations may
not be an adequate approach. However, it was not feasible
to focus separately on each as there were only ten studies
included. Therefore, we performed a sensitivity analysis for
each subgroup after providing the pooled results for the
whole population.
Fourth, we only assessed the per-patient performance
because of the paucity of studies providing per-lesion
results. Per-patient analysis could be expected to result in
better diagnostic performance than per-lesion analysis, as
shown in one of the studies included, in which the per-
patient sensitivity was 1.0, compared to 0.56 for per-[3_TD$DIFF]lesion
analysis However, in a recent meta-analysis assessing
the performance of MRI for detection of vertebral
metastasis from various tumors, the sensitivity and
specificity of per-patient (94.1% and 94.2%, respectively)
and per-lesion analysis (90.1% and 96.9%, respectively)
were both excellent Further studies are required to
resolve this controversy.
Fifth, Kim et al stated that prostate-specific antigen and
Gleason score play an important role in clinical staging for
prostate cancer. We agree and do not suggest that MRI
replaces these parameters. Rather, MRI should be compre-
hensively used with them. In fact, a recent study showed
that when MRI is incorporated in Partin estimates and
CAPRA scores, the performance of clinical staging can be
significantly improved
Conflicts of interest: The authors have nothing to disclose.
References
[1] Woo S, Suh CH, Kim SY, Cho JY, Kim SH. Diagnostic performance of
magnetic resonance imaging for the detection of bone metastasis in
prostate cancer: a systematic review and meta-analysis. Eur Urol.[1_TD$DIFF] In
press. .
[2]
[2_TD$DIFF]
.
[3]
[4]
available at
journal homepage:
DOIs of original articles: .
0302-2838/# 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.