scoring system for prediction of lymph node metastasis in radical cystectomy cohort
TRANSCRIPT
UROLOGY - ORIGINAL PAPER
Scoring system for prediction of lymph node metastasis in radicalcystectomy cohort
Miroslav M. Stojadinovic • Rade Prelevic •
Arso Vukicevic
Received: 12 November 2013 / Accepted: 11 January 2014
� Springer Science+Business Media Dordrecht 2014
Abstract
Objectives The objective of the study was to assess
whether pretreatment clinical parameters combined with
computed tomography can improve the prediction of
lymph node metastasis in patients with bladder cancer
treated with radical cystectomy.
Patients and methods In a single-center retrospective
study, demographic and clinicopathological information
(initial transurethral resection [grade, stage, multiplicity of
tumors, lymphovascular invasion], hydronephrosis,
abdominal and pelvic computed tomography) and the
presence of lymph node disease on final pathology of 183
patients with bladder cancer undergoing radical cystectomy
and pelvic lymph node dissection were reviewed. Logistic
regression and bootstrap methods were used to create an
integer score for estimating the risk of positive lymph
nodes. Various measures for predictive ability and clinical
utility were determined.
Results On pathological examination, 59.6 % of patients
had positive lymph nodes. In a multivariable analysis,
status lymph nodes on computed tomography and hydro-
nephrosis were the most strongly associated predictors. The
resultant total possible score ranged from 0 to 10, with a
cut-off value of [4 points. The area under the receiver
operating characteristic curve was 0.806. Relative inte-
grated discrimination improvement was 14.3 %. In the
decision curve analysis, the model provided net benefit
throughout the entire range of threshold probabilities.
However, the final model was roughly equivalent to using
the clinical exam.
Conclusions The pre-cystectomy scoring system
improved the prediction of lymph node status in patients
with bladder cancer. Our model represented a user-friendly
staging aid, but a large multi-center study should be per-
formed before widespread implementation.
Keywords Bladder cancer � Lymph nodes metastasis �Prognostic model � Scoring system
Abbreviations
AUC Area under the receiver operating characteristic
curve
BC Bladder cancer
CI Confidential interval
CT Computed tomography
ePLND Extended pelvic LND
IDI Integrated discrimination improvement
IP The integrated 1-specificity
IS The integrated sensitivity
LN Lymph node
LND Lymph node dissection
LVI Lymphovascular invasion
MRI Magnetic resonance imaging
MI Muscle-invasive
NC Neoadjuvant chemotherapy
NPV Negative predictive value
NRI Net reclassification improvement
ORs Odds ratios
M. M. Stojadinovic (&)
Department of Urology, Clinic of Urology and Nephrology,
Clinical Centre ‘‘Kragujevac’’, Zmaj Jovina 30,
34000 Kragujevac, Serbia
e-mail: [email protected]
R. Prelevic
Clinic of Urology, Military Medical Academy,
Belgrade, Serbia
A. Vukicevic
Faculty of Engineering, University of Kragujevac,
Kragujevac, Serbia
123
Int Urol Nephrol
DOI 10.1007/s11255-014-0645-x
pN? Lymph node metastases
ROC The receiver operating characteristic curve
PPV Positive predictive value
TUR Transurethral resection
TURBT Transurethral resection of bladder tumor
Introduction
Bladder cancer (BC) represents the fourth most common
cancer in men and the eighth most common malignancy in
women worldwide. About 30 % of patients present with a
muscle-invasive (MI) disease at the time of diagnosis [1].
MIBC spread from the bladder in a predictable stepwise
manner to the lymph nodes (LNs) and then to visceral
organs.
Identifying nodal disease in BC patients is critical
because it has profound implications for treatment plan-
ning [2]. The incidence of positive LNs in radical cys-
tectomy (RC) specimens is between 18 and 30 % [3].
Today, pretreatment assessment of lymph node status is
mainly based on imaging techniques like computed
tomography (CT) and magnetic resonance imaging (MRI)
with contrast enhancement, both of which are recom-
mended by current guidelines [1]. The major shortcoming
of this standard routine is the lack of accuracy and the
evident discrepancy between clinical and pathologic
staging. The assessment of metastases to LNs based
simply on size is limited by the inability of both CT and
MRI to identify metastases in normal-sized or minimally
enlarged nodes. The sensitivity for detection of LN
metastases is low, ranging from 48 to 87 %. Specificity is
also low as nodal enlargement may be due to benign
disease [4]. To overcome these deficiencies, several new
techniques are currently being studied. Although encour-
aging initial reports on new techniques, it will take time
to validate the results before these new approaches can be
integrated into clinical routine [1].
Consequently, clinical prediction has evolved from
physician judgment alone and novel imaging modalities to
risk group stratification, prediction models based on mul-
tivariate regression or principal component analysis, to
nomograms and decision tree model [5–10]. Several recent
studies have demonstrated that multivariate models are
more accurate than most informative single predictors [5–
10].
Based on these considerations, the objective of the study
was to assess whether pretreatment clinical parameters in
combination with CT expressed in scoring system could
improve the prediction of LN status in patients with BC
treated with RC and lymph node dissection (LND).
Patients and methods
Patient population
We retrospectively reviewed the medical records of 248
patients who had undergone radical surgery for BC at
Military Medical Academy, from January 2002 through
December 2012. For each patient, comprehensive clinical
and pathologic information were collected as regards pre-
cystectomy assessment. Patients underwent a routine cys-
toscopic and upper tract evaluation, physical examination,
transurethral resection (TUR) of bladder tumor (TURBT)
or biopsy, abdominal and pelvic CT and chest radiography.
No patient received radiotherapy or neoadjuvant chemo-
therapy (NC) before radical cystectomy. Patients with non-
urothelial BC, or incomplete data, or distant metastatic
disease at the time of cystectomy were excluded. The study
included only patients with at least 9 lymph nodes removed
as suggested previously [11] or less, but they were positive.
Thus, 183 patients were included in the present analyses.
Primary RC or secondary RC (after failure of conser-
vative management of superficial BC) has been defined as
described previously [12]. Tumor size and number were
defined according to preoperative radiological examina-
tions. Evaluation for the presence of hydronephrosis, if
any, was performed in all patients and defined as described
previously [13]. Data about TUR stage and grade were
collected and classified according to the seventh edition
TNM classification system and the 1973 WHO grading
system, respectively, as all other surgical specimens [14,
15]. Lymphovascular invasion (LVI) in TURBT or biopsy
specimens was defined as the unequivocal presence of
tumor cells within an endothelium-lined space, with no
underlying muscular walls [16]. The time period between
TURBT and RC was measured as the number of months
from date of TURBT to date of RC. Status of lymph nodes
was evaluated on the basis of size, texture, morphology and
intensity of the signal. Status LNs on CT were categorized
into two main groups. The first group represents patients
with no LNs involvement or the presence of LNs with a
shot axis of\10 mm, ‘‘nonpathologic’’. The second group,
‘‘pathologic’’, was considered when a nodal enlargement
(C10–20 mm in the long axis) was depicted [17].
All patients underwent radical cystectomy, pelvic lym-
phadenectomy and urinary diversion. Bilateral lymphade-
nectomy was performed at least in the obturator fossa and
along the internal and external iliac artery. The indications
for radical cystectomy were tumor invasion into the mus-
cularis propria or prostatic stroma or Ta, T1, or carcinoma
in situ refractory to TUR with intravesical chemotherapy
and/or immunotherapy. The extent of LND was at the
surgeon’s discretion, and extended pelvic LND (ePLND)
was not routinely performed.
Int Urol Nephrol
123
Outcome variable
The presence of lymph node metastases (pN?) in surgical
specimen after pathological review was the primary inter-
est of statistical analysis.
Statistical analyses
Univariate and multivariate regression was used to identify
and quantify the independent predictors of pN?. The
results of regressions were expressed in odds ratios (ORs)
with 95 % confidential interval (CIs). To examine the
stability of the model’s effect estimates and check for over-
fitting, we used the bootstrap method to generate 1,000
samples. The medians of the resultant beta coefficients for
each variable were then reported and used to develop an
integer-based weighted point system. Then the resultant
beta coefficients were multiplied by 15 and rounded off to
the nearest integer. Individual scores were assigned to each
patient-discharge record by summing the individual risk
factor points. The cut-off points for predicting pN? were
identified. Sensitivity, specificity, positive predictive value
(PPV), negative predictive value (NPV) and accuracy for
scoring systems were determined. Different aspect of per-
formance and utility risk prediction model was assessed
using the Hosmer–Lemeshow statistic, calibration and
Nagelkerke’s R2 for model fit, the area under the receiver
operating characteristic (ROC) curve (AUC) and integrated
discrimination improvement (IDI) for predictive ability,
and decision curve analyses for clinical utility [18–20].
Assumption was made that the identification of pN? would
lead to treatment with NC. The interpretation of a decision
curve was that the model with the highest net benefit at a
particular threshold probability should be chosen.
Statistical significance was set at p \ 0.05. All analyses
were performed using SPSS version 10.0 (SPSS Inc.,
Chicago, IL), MATLAB 2010a software (MathWorks,
Natick, MA), and R-statistics (the R foundation for Sta-
tistical Computing, version 2.15.1).
Results
Patients’ characteristics
The mean ± standard deviation (range) patient age at the
time of cystectomy was 63.4 ± 9.0 (42–86) years and 166
(90.7 %) patients were male. Of all the patients, 77
(42.1 %) presented with no, 61 (33.3 %) unilateral and 45
(24.6 %) bilateral hydronephrosis. TUR was performed in
149 (81.4 %) patients, median (IQR; range) 2 (1; 1–12)
months before RC. The pathological staging after RC of
the entire cohort was distributed as follows: 9 (4.9 %)
patients had T1, 52 (28.4 %) had T2, 73 (39.9 %) had T3,
and 49 (26.8 %) had T4 disease. On CT 76 (41.5 %) of
patients had LN status defined as group one, 107 (58.5 %)
had status defined as group two or ‘‘pathologic’’. The
median (IQR; range) number of removed LNs was 14 (8;
2–25). Overall, 109 (59.6 %) patients had LN metastases,
median 3 (IQR; range) (3; 1–11). Pearson’s r for rela-
tionship between pathological stages with lymph node
metastases was 0.565, p = 0.000. After histological eval-
uation, the absence of tumor involvement was correctly
diagnosed in 53 of 76 patients (69.7 %) in group one, and
in 21 of 107 ones (19.6 %) in group with ‘‘pathologic’’ LNs
by CT (Pearson v2 = 46.329, p = 0.000). The clinico-
pathological characteristics of the patient cohorts (pN- or
pN?) are shown in Table 1.
Table 1 Baseline patients’ clinicopathological characteristics in lymph node-negative and positive bladder cancer (n = 183)
Characteristics LN negative LN positive p value
Age, years 62.7 ± 10.1 63.9 ± 8.2 0.364
Gender, female/male [n (%)] 6/68 (8.1/91.9) 11/98 (10.1/89.9) 0.797
Primary/secondary [n (%)] 41/33 (55.4/44.6) 58/51 (53.2/46.8) 0.880
Size of tumors (cm)a 3.3 5.3 0.000
Number of tumors, 1, 2 or C3 [n (%)] 13/12/49 (17.6/16.2/66.2) 15/16/78 (13.8/14.7/68.5) 0.717
Initial tumor grade 2 or 3 [n (%)] 14/60 (18.9/81.1) 8/101 (7.3/92.7) 0.017
Initial tumor TUR stage Ta/T1/T2 [n (%)] 3/23/48 (4.1/31.1/64.9) 3/16/90 (2.8/14.7/82.6) 0.022
Lymphovascular invasion no/yes [n (%)] 29/45 (39.2/60.8) 22/87 (20.2/79.2) 0.004
Hydronephrosis no/unilateral/bill [n (%)] 45/25/4 (60.8/33.8/5.4) 32/36/41 (29.4/33/37.6) 0.000
Status LN on CT [n (%)] 53/21 (71.6/28.4) 23/86 (21.1/78.9) 0.000
Pathological stage Ta/T1, T2, T3, T4 [n (%)] 9/41/17/7 (12.2/55.4/23/90.5) 0/11/56/42 (0/10.1/51.4/38.5) 0.000
LN lymph node, CT computed tomographya Median, interquartile range
Int Urol Nephrol
123
Prediction and scoring system for pN?
In a univariate analysis, 6 risk factors displayed significant
correlation with pN? (Table 2). During multivariable
analysis, two sustained their prognostic significance
(Table 2). The analysis demonstrated the status of LNs on
CT and hydronephrosis have strong prognostic value of
pN? (Table 2). All variables maintained significance in the
bootstrap model (Table 2).
Next, a total score was calculated by summing the points
from each variable for each patient. The resultant total
possible score ranged from 0 to 10, with a cut-off value of
[4 points. AUC for the scoring system was 0.806 (95 %
CI 0.743–0.870), showing the model to have good dis-
criminatory ability and significantly better (difference
between areas 0.0539, p = 0.0008) compared when model
include only prediction of status LNs on CT (AUC 95 %
CI 0.753, 0.678–0.827) (Fig. 1). The sensitivity and spec-
ificity of the scoring system in the data set were 0.826
(95 % CI 0.741–0.892) and 0.676 (95 % CI 0.557–0.780),
respectively. The calculated PPV, NPV and accuracy were
0.789 (95 % CI 0.703–0.860), 0.725 (95 % CI
0.604–0.825) and 0.765 (95 % CI 0.697–0.824), respec-
tively. Graphical assessments of score calibration are pre-
sented in Fig. 2. The scoring system was well calibrated
because of the Hosmer and Lemeshow goodness of fit test
statistic was v2 = 6.537, p = 0.163, thereby demonstrating
good fit. The Brier score for a model was 0.171. The
Nagelkerke’s R2 value in the model was 0.363.
IDI and summary statistics are shown in Table 3. Rel-
ative improvement with new model was 14.3 %. The risk
assessment plot is shown in Fig. 3. Only the IDIevents was
small with a 95 % CI that straddled zero. The model
overall similarly identifies those who do not have events
(the nonevents curve, integrated 1-specificity [IPnew] =
0.359) and those who do (the events curve, integrated
sensitivity [ISnew] = 0.657). The addition of hydrone-
phrosis to the model makes very little difference. Fur-
thermore, reference and new model curve partly overlaps.
The IS and IP have positive and negative components.
Positive between a risk of 0.30–0.58 and between 0.80 and
0.90, and negative from 0.23 to 0.30 and between 0.66 and
0.80. Nevertheless, the resulting net for IS and IP were
0.0146, p = 0.014, and 0.0221, p = 0.001, respectively.
In the decision curve analysis (Fig. 4), both model and
clinical exam predicting pN? provided net benefit
throughout the entire range of threshold probabilities above
30 % as compared to the strategy of treating all patients
with NC, or alternatively, treating no one. The graph shows
that the final model (dotted black line) is roughly equiva-
lent to using the clinical exam (dotted red line) alone
between 30 and 80 % threshold probabilities.
Discussion
Pretreatment identifying lymph node metastasis could
improve decision-making for NC that is associated with a
potential benefit for this group of patients, extended lym-
phadenectomy, or conservative management. In the current
study, we have taken a unique approach for prediction LNs
status before RC using clinicopathological features
obtained before radical surgery. Our scoring system was
able to achieve an accuracy of 76.5 %. The tool showed
satisfactory discrimination, calibration, and clinical use-
fulness in the internal validation.
To date, several clinicopathological factors are reportedly
associated with post-surgical pathological stage and were
included in the existing models such as TUR parameters of
stage and grade [5–7, 9, 10], LVI [5, 6, 8], hydronephrosis [6,
8–10], age [6, 7, 10], female gender [7, 21], CIS [7], histo-
logical variants [21], tumor size [9], tumor growth pattern
[10], multiplicity of tumors [8, 10], palpable mass [8], number
of intravesical treatments [8], NC [7], primary versus sec-
ondary RC [12], oncofetal markers [9], preoperative plasma
soluble E-cadherin [22], expression of vascular endothelial
growth factor-C [23], or gene expression model on primary
tumor tissue [24]. In line with previous studies, several of
those factors have reached statistical significance in the uni-
variate or multivariate analysis in our model. However, many
Table 2 The analysis of possible and independent predictors for lymph nodes metastasis in bladder cancer patients and point value
Factor Univariate analysis Multivariable analysis Bootstrap Point value
OR (95 % CI) p value OR (95 % CI) p value B B
Size of tumors 1.393 (1.176–1.651) 0.000
Initial tumor grade 2.946 (1.167–7.433) 0.022
Initial tumor stage 2.033 (1.134–3.644) 0.017
Lymphovascular invasion 2.548 (1.316–4.935) 0.006
Hydronephrosis 3.138 (2.006–4.909) 0.000 2.113 (1.298–3.440) 0.003 0.748 0.133 2
Status LN on CT 9.437 (4.764–18.691) 0.000 6.448 (3.131–13.281) 0.000 1.864 0.409 6
LN lymph node, CT computed tomography
Int Urol Nephrol
123
of these parameters did not retain their independent predictive
value, even those with previously proved significance [25].
Small sample size in our study could, at least partially, explain
the observation. Nevertheless, we found that unilateral and
bilateral hydronephrosis was a strong independent predictor of
pN?. These findings support those of previous investigators
such as Stimson et al. [26], who reported that preoperative
hydronephrosis was independently associated with extrave-
sical and node-positive disease at the time of cystectomy,
directly affecting cancer-specific survival and predicted the
side of nodal involvement.
In our study,[59 % of patients harbored LN metastasis
because in our cohort, locally advanced BC dominated
(66.7 %), contrary to other study were organ-confined BC
dominated. In accordance with previous results, the pro-
portion of having a positive LNs increased proportionally
with advancing pathologic T stage [25]. Our study support
findings that currently available standard techniques based
simply on size is still not accurate enough to predict
pathologic node-negative disease in patients with MIBC
[1], because small lymph nodes can contain tumor (about
30 % in our study) and enlarged nodes may be reactive but
may not contain tumor (about a fifth in our study). More-
over, metastases from bladder and other pelvic cancers
frequently cause very little nodal enlargement, and the
round shape of the LNs are more likely to be metastatic
than are ovoid nodes [2].
In 2006, Karakiewicz published the first nomograms for
predicting pT3-4 and pN? disease in BC [7]. Their model
indicated an accuracy of 63.1 % for pN? disease. How-
ever, a recent validation study in European patients dem-
onstrated a notable decrease in model performance (the
AUC was 54.5 % for pN? disease) which remains similar
after refitting the model (64.7 % for pN? disease) [27].
Our scoring system resulted in an AUC of 80.6 %, which is
statistically better than the model that only included vari-
ables proposed by Karakiewicz’s report and similar other
reports (67–85 %) [5, 6, 8, 9, 24].
Integration of risk factors into decision tools is neces-
sary to provide patients and physicians with individualized
need to implement NC. However, in bladder cancer, there
are many unresolved issues regarding the NC, and thus, the
threshold probability of clinical application remains an
open question. First of all, NC prior to cystectomy has not
been widely adopted, since most patients do not benefit,
Fig. 1 ROC curves analysis of scoring system and status lymph
nodes on computed tomography for predicted lymph node-positive
bladder cancer
Fig. 2 Observed versus predicted probability for lymph node-
positive bladder cancer by score
Table 3 IDI and summary
statistics
IDI the integrated
discrimination improvement, IS
the integrated sensitivity, IP the
integrated 1-specificity, events
lymph nodes positive, nonevents
lymph nodes negative, ref
reference model, new new
model
Metrics of IDI Mean (95 % CI) p value
IDIevents 0.0146 (-0.0044 to 0.0337) 0.131
IDInonevents 0.0216 (0.0003 to 0.0428) 0.047
IDI Absolute 0.0367 (0.0238 to 0.0496) 0.000
ISref (reference) 0.6971 ((0.6657 to 0.7285) \0.0001
ISnew (reference ? hydronephrosis) 0.7117 (0.6848 to 0.7385) \0.0001
IS 0.0146 (0.0030 to 0.0261) 0.014
IPref (reference) 0.445 (0.4115 to 0.4785) \0.0001
IPnew (reference ? hydronephrosis) 0.4229 (0.392 to 0.4537) \0.0001
IP 0.0221 (0.0088 to 0.0355) 0.001
IDI relative 14.3 %
Int Urol Nephrol
123
and we are currently unable to predict those that do. Then,
there is a concern for delay of surgery and risk of disease
progression [26]. Furthermore, a strict statistical correla-
tion between clinical tumor stage and effectiveness of NC
was not described. Available studies suggest a much more
substantial benefit for patients with high-risk disease (cT3,
cT4a) and/or lymph node-positive disease (cN1) [28]. One
simple way to test the clinical consequences of using pre-
diction tools is to use decision curve analyses for clinical
utility. Based on these considerations, we considered the
relevant range of threshold probabilities to be about
20–50 %. In this range, decision curve analysis of our
model including both status LNs on CT and hydronephrosis
offers the highest net benefit both for clinicians hesitant to
use NC and for those who liberally recommend for its use.
However, it remains an open question selection of those
most likely to benefit from NC, while avoiding overtreat-
ment and delay.
The current study has several limitations worth noting.
First, enrolled patients were retrospectively collected in a
single tertiary center with a relatively small patient cohort
who may influence the results by the selection bias. Sec-
ond, pN? is a useful diagnostic marker but predicting
disease outcome, surveillance or response to therapy is
more clinically significant. A third limitation of the study is
the exclusion of other possible risk factors for advanced
disease, such as biomarkers [9], bimanual palpations (BP)
[29]. These data were not available in our cohort. In our
study, the extent of LND was at the surgeon’s discretion,
and ePLND was not routinely performed. Therefore, we
used the threshold of 9 LNs removed, as the minimum
number required during LND [11]. Furthermore, it was
found that there was a weak correlation between the
number of retrieved nodes and number of positive nodes
[25, 30]. However, the number of LNs removed is not only
a factor of the extent of LND, but is also dependent on the
pathological evaluation, inherent differences among
patients, the location of LNs from an area with a high
likelihood of malignancy [11], recently established clinical
nodal staging score [31], and the pathological nodal staging
score [32]. We used the scoring system approach as we are
very familiar with it in both routine work and in the
research. However, other prognostic tools are also possible
(e.g., nomograms) according to the individual preferences
and study goals. Furthermore, our models are not appli-
cable to patients who were pretreated with radiotherapy or
to those harboring pathologies other than transitional cell
carcinoma. Finally, we used a bootstrap method internal
validation and did not use an external cohort to validate our
scoring system. Nevertheless, to our knowledge, this is the
first study that prognostic model expressed in scoring
system, a user-friendly staging aid, to predict pathological
node status before surgery. The prediction model repre-
sents another step toward accurately estimating individu-
alized risk of LNs metastases in a patient population
lacking optimal staging procedures.
Conclusions
We developed a scoring system to predict the pathological
node status in BC patients treated with RC by evaluating
Fig. 3 The risk assessment plot. The reference risk models (dashed
lines) and new risk models (solid lines) were obtained by addition of
hydronephrosis for prediction lymph node-positive bladder cancer.
Red lines represent 1-specificity versus the calculated risk for those
with the event; black lines are sensitivity versus the calculated risk for
those without events
Fig. 4 Decision curve analysis of the effect of prediction models on
the detection of lymph node-positive status. Net benefit is compared
with ‘‘NC for all’’ strategy and ‘‘NC for none’’. Model 1 is a final
model including status lymph nodes on CT and hydronephrosis
(dotted black line). Model 2 is a model including only status lymph
nodes on CT (dotted red line)
Int Urol Nephrol
123
the status LNs on CT and the presence of hydronephrosis.
The newly devised formula has an accuracy of 76.5 % and
was internally validated. Adoption of such a tool into daily
clinical decision-making may lead to more appropriate
integration of perioperative NC, thereby potentially
improving survival in patients with BC. The clinical value
of this model needs to be further assessed in external multi-
institutional validation cohorts.
Acknowledgments The authors were financially supported through
a research grant N0175014 of the Ministry of Science and Techno-
logical Development of Serbia. The authors thank the Ministry for
this support.
Conflict of interest None.
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