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tumor involvement proved higher than those of systematic
biopsy. Only older age was independently associated with
any upgrading by MRI-ultrasound fusion biopsy. High MRI
suspicion score was closely aligned with upgrading in
targeted cores.
Smaller series have attempted to define the detection
yield of MRI-ultrasound fusion biopsy during AS. Walton
Diaz et al
[16]reported on a cohort of patients who
underwent diagnostic and follow-up MRI-ultrasound fusion
and systematic biopsies. Confirmatory biopsy resulted in
upgrade to GS 7 in 22% of patients, of whom 35% (12 of 34)
had detection with MRI-ultrasound fusion alone compared
with 29% (10 of 34) who had detection with systematic
biopsy. Of note, all patients in their study received MRI-
ultrasound fusion biopsy at enrollment, whereas we
described a large cohort of patients enrolled in AS on the
basis of low- and intermediate- risk clinical features with
only prior systematic biopsy, a population in which methods
of additional risk assessment remain vigorously debated.
Among our cohort, pathological upgrade was detected in 14%
on the basis of MRI-ultrasound fusion cores alone, indicating
a potential role for improving the detection of high-grade
cancers, even among men with a prior positive biopsy.
Given the favorable detection rates associated with MRI-
ultrasound fusion biopsy cores, growing speculation about
foregoing additional systematic sampling for men with
prior biopsies has emerged. Our study detected a small, yet
notable number of cases (9%) in which systematic biopsy
detected tumors with GS 4 + 3 in men with negative MRI-
ultrasound fusion biopsies.
It remains unclear how best to reconcile clinical data
derived from improved sampling techniques with current
risk stratification tools. Of particular relevance to AS is
tumor volume prediction, which has been validated for
systematic sampling but is likely to be higher with image-
guided techniques
[17]. Within our findings, MRI-ultra-
sound fusion cores obtained a median maximum tumor
involvement of 40% (IQR: 20–64%) compared with 31% (IQR:
14–50%) with systematic biopsy. Similarly, Abdi et al
[18]found that targeted cores contained more tumor than
systematic samples, and they recommended caution when
using such results for risk stratifying patients according to
existing guidelines. Indeed, adherence to strict AS inclusion
criteria may disqualify otherwise low-risk patients on the
basis of volume or number of cores positive on MRI-
ultrasound fusion biopsy. Additional investigation is
warranted to assess the validity of clinical prediction tools
using novel biopsy methods.
We examined the associations among clinical and
pathological variables with upgrading on MRI-ultrasound
fusion biopsy from concurrent systematic cores, where
older age was associated with any upgrading (OR: 1.10; 95%
CI, 1.01–1.20;
p
= 0.03). Among patients undergoing AS,
Anderson et al
[19]also determined that older patients had
increased odds of upgrading on confirmatory biopsy.
Whereas number of previous biopsy sessions was not
significantly associated with primary outcomes (OR: 0.65;
95% CI, 0.409–1.021;
p
= 0.06), previous studies from
our institution have shown that a greater number of
surveillance biopsies was associated with lower risk of
upgrading
[20,21]. Our studies suggest that MRI-ultrasound
fusion biopsy may be beneficial for older patients, but the
magnitude of benefit may decrease for patients with stable
disease.
In addition, higher MRI suspicion scores (4–5 vs 1–3)
were closely aligned with upgrading on MRI-ultrasound
fusion biopsy. Suspicion scores were high (4/5) for all but
two patients who experienced any upgrading and for all
patients with major upgrading. This observation appears
consistent with prior studies examining MRI findings and
risk of cancer upgrading
[[7_TD$DIFF]
22–[8_TD$DIFF]
25].
This study has several limitations, including the retro-
spective design and performance at a single tertiary care
institution, which may limit generalizability. In addition,
not all patients received mpMRI studies in the same time
frame during surveillance, with some receiving baseline
evaluations and others following years of surveillance.
While clinicians performing the biopsies adhered to a
prespecified extended-sextant sampling technique, they
were not blinded to imaging findings and we did not change
operators between MRI-ultrasound fusion and systematic
biopsies. We lacked complete information regarding the
location of mpMRI lesions in relation to prior biopsy sites,
which restricted a potentially important analysis compar-
ing the two.
5.
Conclusions
MRI-ultrasound fusion biopsy increased the detection of GS
upgrading in patients managed with AS, as it detected a
number of high-risk tumors missed by concurrent system-
atic biopsy. Systematic biopsy alone also detected such
tumors among cases where MRI-ultrasound fusion results
were negative. Clinicians and patients may consider
obtaining both targeted MRI-ultrasound fusion and sys-
tematic biopsy cores to maximize detection of upgraded
PCa. Future investigation is warranted to determine distant
outcomes attributable to MRI-ultrasound fusion biopsy use
and its applicability with current guidelines.
Author contributions:
Geraldine N. Tran 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:
Tran, Leapman, Carroll.
Acquisition of data:
Tran, Leapman, Nguyen, Cowan, Shinohara, West-
phalen.
Analysis and interpretation of data:
Tran, Cowan.
Drafting of the manuscript:
Tran, Leapman, Cowan, Westphalen.
Critical revision of the manuscript for important intellectual content:
Tran,
Leapman, Nguyen, Westphalen, Carroll.
Statistical analysis:
Cowan.
Obtaining funding:
Carroll.
Administrative, technical, or material support:
Tran, Nguyen, Cowan,
Shinohara.
Supervision:
Carroll.
Other (specify):
None.
Financial disclosures:
Geraldine N. Tran certifies that all conflicts of
interest, including specific financial interests and relationships and
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