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1.
Introduction
The widespread use of routine abdominal
imaging has
led
to
an
increase
in
the
proportion
of
patients
diagnosed
with
asymptomatic
small
renal masses
(SRMs)
[1] .According
to
National
Comprehensive
Cancer
Network
and
European
Association
of
Urology
guidelines,
partial
nephrectomy
represents
the standard of care
for
these patients
[2,3]. Min-
imally
invasive partial nephrectomy
(MIPN),
including both
laparoscopic
and
robot-assisted
approaches,
has
emerged
as
an
effective
alternative
to
open
surgery,
offering
comparable
oncologic
outcomes
with
reduced
morbidity
[4–7].
Several
thermal
ablation
procedures
have
been
devel-
oped
to
reduce
the
risk
of
complications.
Thermal
ablation
has
several potential benefits
compared
to partial nephrec-
tomy, as
there
is no need
to
incise the renal parenchyma and
to
clamp
vessels.
Among
alternative
ablative
strategies,
laparoscopic
renal
cryoablation
(LRC) has
shown encourag-
ing
oncologic
outcomes
[8,9]and
lower
retreatment
rates
[10].
Several
studies
have
compared
partial
nephrectomy
to
LRC
for
SRM
treatment.
Specifically,
LRC
was
associated
with
lower
complication
rates,
good
functional
outcomes,
and
higher
recurrence
rates
compared
to
laparoscopic
partial nephrectomy
[11,12]. Similar results emerged
from a
comparison
of
LRC
and
robot-assisted partial nephrectomy
[13].
These
findings were
substantially
confirmed
by
two
recent
meta-analyses
that
highlighted
worse
oncologic
outcomes
and
improved
perioperative
outcomes
for
LRC
compared
to
laparoscopic
partial
nephrectomy
[14,15].
However,
these
studies
analyzed
minimally
invasive
surgery and LRC
in highly heterogeneous patient population,
including
cancer-naı¨ve patients,
single-kidney patients,
and
patients with previous surgery
for kidney cancer. As previous
history
of
renal
cell
carcinoma
(RCC)
is
an
important
predictor of adverse oncologic outcomes
[16] ,such
studies
are
prone
to
selection
bias
[17] .Moreover,
in
patients
previously
treated with
renal
surgery, both MIPN
and
LRC
might
be more
challenging,
resulting
in
poorer
surgical
and
functional
outcomes.
We
hypothesized
that
MIPN
and
LRC
would
lead
to
similar outcomes
in a more homogeneous group of patients
less
susceptible
to
selection
bias,
specifically,
patients
newly
diagnosed with
a
single
SRM. We
used
our
single-
institution
database
to
compare
intraoperative,
periopera-
tive, oncologic, and
functional outcomes of MIPN and LRC
in
this
study
population.
2.
Patients
and methods
2.1.
Patient
population
After
institutional
review board approval, we
identified 412 consecutive
patients diagnosed with an SRM
( 4
cm) and
treated with either MIPN or
LRC
at
our
institution
between
2000
and
2013. We
excluded
patients
with
a
previous
history
of
RCC
(
n
= 16),
patients with
a
solitary
kidney
(
n
= 11),
and
patients
diagnosed
with
synchronous
lesions
(
n
= 13).
These
selection
criteria
yielded
372
assessable
individuals
newly
diagnosed with a single SRM. Treatment choice was
left
to
the discretion
of
the
surgeon. MIPN was
typically proposed
for healthy young patients
who elected
for nephron-sparing surgery. Conversely, LRC was offered
to
patients with comorbidities and baseline
renal dysfunction, who were at
higher
surgical
risk. Three different
surgeons, who
started
their
surgical
experience at our
institution,
treated all
the
cases. Patients were
treated
during
the
surgeons’
learning
curve,
and
the
three
surgeons
performed
MIPN
and
LRC during
the
same period. Overall, 166 patients
(45%) were
treated by surgeon #1, 140
(37%) by surgeon #2, and 66
(18%) by surgeon
#3. Surgeons #1, #2, and #3 performed 101
(49%), 84
(41%), and 21
(10%)
procedures
in
the MIPN
group,
and
65
(39%),
56
(34%)
and
45
(27%)
procedures
in
the
LRC
group,
respectively.
2.2.
Surgical
techniques
Minimally
invasive
surgery
consisted
of
either
laparoscopic
or
robot-
assisted
partial
nephrectomy
performed
using
previously
described
surgical
techniques
[18,19]. Specifically,
intraoperative ultrasonography
was
carried out
in all patients
to guide
tumor
excision,
the
renal vessels
were
clamped,
and
partial
nephrectomy
was
completed
under
warm
ischemia.
LRC
consisted
of
transperitoneal
or
retroperitoneal
access
to
the
renal
cavity, kidneymobilization,laparoscopic ultrasoundevaluation, ultrasound-
guided
biopsy
of
the
lesion,
puncture
of
the
SRM with
cryoprobes,
and
a
double
freeze-thaw cycle with extension of
the
ice ball approximately 1 cm
beyond
the
tumor
edge
[20] .2.3.
Patient
variables
We
collected
data
for
the
following
variables:
age
at
diagnosis,
gender,
American
Society
of
Anesthesiologists
(ASA)
score,
body
mass
index
(BMI),
preoperative
serum
creatinine,
preoperative
estimated
glomeru-
lar
filtration
rate
(eGFR),
chronic
kidney
disease
stage,
tumor
size,
and
tumor
location
(side,
pole,
and
face).
eGFR
was
calculated
using
the
equation
from
the Modification
of
Diet
in
Renal
Disease
Study
Group
[21]. Chronic kidney disease
stage was defined according
to
the National
Kidney
Foundation
clinical
practice
guidelines
[22].
2.4.
Outcomes
and
statistical
analysis
The
aim
of
the
study was
to
compare MIPN
and
LRC
in
patients
newly
diagnosed
with
a
single
SRM. We
hypothesized
that
MIPN
and
LRC
provided
similar
results
regarding
the
following
outcomes.
2.4.1.
Intraoperative
and
perioperative
outcomes
We
evaluated
estimated
blood
loss,
total
operative
time,
intraoperative
complications, blood
transfusion
rate,
in-hospital complications, Clavien-
Dindo
complication
grade
[23],
and
length
of
hospital
stay.
Linear
and
logistic regressionswere used to evaluate the
impact of surgical treatment
(MIPN
vs
LRC)
on
continuous
and
binary
outcomes,
respectively.
Data
were adjusted
for patient age, ASA
score
(1 vs 2 vs 3), and
tumor
size. For
the
endpoints
of
intraoperative
complications,
blood
transfusion
rate,
and
Clavien-Dindo
complication
grade,
event
numbers were
low,
so we
adjusted
only
for ASA
score.
2.4.2.
Oncologic
outcomes
We evaluated
the
local
recurrence
rate, metachronous SRM
rate, distant
metastasis
rate,
and
disease-free
survival
rate.
Local
recurrence
was
defined
as
an
enlarging
or
persistently
enhanced
treatment
site
on
follow-up
imaging,
according
to
Working
Group
on
Image-guided
Tumour Ablation
criteria
[24]. Metachronous SRM was defined as a new
contrast-enhancing
lesion
located at a
site other
than
the
treated area
in
the
ipsilateral
kidney
or
in
the
contralateral
kidney. Distant metastasis
was
defined
as
the
presence
of
RCC
anywhere
else
apart
from
the
ipsilateral
or
contralateral
kidney. Disease-free
survival was
defined
as
the
simultaneous
absence
of
local
recurrence, metachronous
SRM,
and
E U R O P E A N
U R O L O G Y
F O C U S
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