68 96
distant
metastasis.
Follow-up
of
MIPN
patients
consisted
of
either
a
computed
tomography
scan
at 6 mo
and yearly
thereafter
in
the
case of
histologic
diagnosis
of
RCC,
or
ultrasound
sonography
in
the
case
of
benign
SRM.
Follow-up
of
LRC
patients
involved
either
serial magnetic
resonance
imaging at 3, 6, and 12 mo and yearly
thereafter
in
the case of
biopsy-proven RCC
or unknown histology,
or ultrasound
sonography
in
the
case
of
biopsy-proven
benign
SRM. Kaplan-Meier
curves were
used
to
estimate
disease-free
survival
rates,
stratifying
patients
according
to
treatment
type
(MIPN
vs
LRC). Cox
regression
analysis was used
to
test
the
association
between
treatment
type
and
disease-free
survival.
Multivariate
analysis
was
not
used
because
of
the
small
number
of
events within
the
two
groups.
2.4.3.
Functional
outcomes
Serum
creatinine was measured
on postoperative
day
1
and
at
3,
6,
and
12mo and yearly thereafter. Kernel-weighted
local polynomial smoothing
methods were used
to determine
the variation and percentage
reduction
in
eGFR
after
surgery
for
the MIPN
and
LRC
groups. Multivariate
linear
regression analysis was used
to evaluate
the
impact of surgical
treatment
(MIPN vs
LRC) on postoperative eGFR
at 6 mo and 3 yr after
surgery. The
covariates were
age
at
surgery,
preoperative
eGFR,
and
tumor
size.
All
statistical
analyses
were
performed
using
Stata
(StataCorp
LP,
College
Station, TX, USA)
version 12.0.
3.
Results
3.1.
Clinical
and
pathologic
characteristics
The
clinical
and
pathologic
characteristics
of
the
patient
population are summarized
in
Table 1. Overall, 206 patients
(55%) underwent MIPN, while 166
(45%) were
treated with
LRC.
In
the
MIPN
group,
97
and
109
patients
received
laparoscopic
and
robot-assisted
partial
nephrectomy,
re-
spectively.
Compared
to
the
LRC
group,
patients
treated
with MIPN were
significantly
younger,
less
comorbid,
and
Table 1 – Clinical
and pathologic
characteristics of 372
consecutive patients newly diagnosed with a
single
small
renal mass and
treated at a
single
tertiary
referral
center
between
2000
and
2013,
stratified
according
to
treatment
type
Variables
MIPN
(
n
= 206)
LRC
(
n
= 166)
p
value
Age
at
diagnosis
(yr)
60
(51–70)
66
(57–73)
0.001
Gender
0.3
Male
141
(68)
122
(73)
Female
65
(32)
44
(27)
ASA
score
<
0.0001
1
52
(25)
17
(10)
2
120
(58)
99
(60)
3
34
(17)
50
(30)
BMI
(kg/m
2
)
26
(23–28)
25
(23–29)
0.8
Serum
creatinine
(mg/dl)
0.87
(0.74–1.00)
0.93
(0.80–1.04)
0.003
eGFR
(ml/min/1.73 m
2
)
83
(72–99)
78
(68–88)
0.001
CKD
stage
0.03
1
73
(35)
39
(23)
2
116
(56)
99
(60)
3
17
(9.0)
28
(17)
Tumor
dimension
(mm)
2.5
(2.0–3.4)
2.0
(1.5–2.5)
<
0.0001
Tumor
side
0.057
Right
105
(51)
101
(61)
Left
101
(49)
65
(39)
Tumor
pole
0.001
Superior
43
(20)
38
(23)
Middle
86
(42)
95
(57)
Inferior
77
(38)
33
(20)
Tumor
face
0.2
Anterior
111
(54)
93
(56)
Posterior
95
(46)
73
(44)
Pathologic
diagnosis
<
0.0001
Malignant
lesion
153
(74)
105
(63)
Benign
lesion
53
(26)
43
(26)
Nondiagnostic
0
(0)
18
(11)
Malignant
type
0.09
Clear
cell
97
(63)
79
(75)
Papillary
38
(25)
22
(21)
Chromophobe
15
(10)
3
(2.9)
Other
3
(2.0)
1
(1.0)
Benign
type
0.07
Oncocytoma
31
(58)
34
(79)
Angiomyolipoma
20
(38)
9
(21)
Other
2
(3.8)
0
(0)
Surgical margins
–
Negative
193
(94)
–
Positive
13
(6.3)
–
MIPN = minimally
invasive
partial
nephrectomy;
LRC =
laparoscopic
renal
cryoablation; ASA = American
Society
of Anesthesiologists;
BMI = body mass
index;
eGFR = estimated
glomerular
filtration
rate;
CKD =
chronic
kidney
disease.
Continuous
data
are
presented
as median
(interquartile
range)
and
categorical
data
as
n
(%).
E U R O P E A N
U R O L O G Y
F O C U S
1
( 2 0 1 5
)
6 6 – 7 2
68