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Froehner et al. BMC Urology 2014, 14:28
http://www.biomedcentral.com/1471-2490/14/28
RESEARCH ARTICLE
Open Access
A combined index to classify prognostic
comorbidity in candidates for radical
prostatectomy
Michael Froehner1*, Anna-Elisa Kellner1, Rainer Koch2, Gustavo B Baretton3, Oliver W Hakenberg4 and Manfred P Wirth1
Abstract
Background: In patients with early prostate cancer, stratification by comorbidity could be of importance in clinical
decision making as well as in characterizing patients enrolled into clinical trials. In this study, we investigated several
comorbidity classifications as predictors of overall mortality after radical prostatectomy, searching for measures
providing complementary prognostic information which could be combined into a single score.
Methods: The study sample consisted of 2205 consecutive patients selected for radical prostatectomy with a mean
age of 64 years and a mean follow-up of 9.2 years (median: 8.6). Seventy-four patients with incomplete tumor-related
data were excluded. In addition to age and tumor-related parameters, six comorbidity classifications and the body mass
index were assessed as possible predictors of overall mortality. Kaplan-Meier curves and Mantel-Haenszel hazard
ratios were used for univariate analysis. The impact of different causes of death was analyzed by competing risk
analysis. Cox proportional hazard models were calculated to analyze combined effects of variables.
Results: Age, Gleason score, tumor stage, Charlson score, American Society of Anesthesiologists (ASA) physical
status class and body mass index were identified a significant predictors of overall mortality in the multivariate
analysis regardless whether two-sided and three-sided stratifications were used. Competing risk analysis revealed
that the excess mortality in patients with a body mass index of 30 kg/m2 or higher was attributable to competing
mortality including second cancers, but not to prostate cancer mortality.
Conclusion: Stratifying patients by a combined consideration of the comorbidity measures Charlson score, ASA
classification and body mass index may assist clinical decision making in elderly candidates for radical prostatectomy.
Keywords: Prostate cancer, Radical prostatectomy, Comorbidity, Overall survival, Competing mortality, ASA
classification, Charlson score, Body mass index, Cox proportional hazard models
Background
Because of the usually slow disease progression and the
competing curative treatment options with different
impacts on quality of life, comorbidity is of particular
clinical importance in men with early prostate cancer
[1,2]. There is, however, no consensus on the best comorbidity classification to use in this situation [3-5]. The
Charlson score [6] has probably been most extensively
studied [4,5,7]. In addition, a multitude of other assessment instruments have been evaluated with, however,
inconclusive results [3,5]. The complementary prognostic
value of different comorbidity classifications has – to our
knowledge – not been demonstrated yet in patients with
early prostate cancer. Stratifying by comorbidity would
be important in clinical decision making as well as in
the characterization of patients enrolled into clinical
trials. In this study, we investigated several comorbidity
classifications as predictors of overall mortality after radical prostatectomy, searching for measures providing
complementary prognostic information which could be
combined into a single score.
* Correspondence: Michael.Froehner@uniklinikum-dresden.de
1
Departments of Urology, University Hospital “Carl Gustav Carus”, Technische
Universität Dresden, Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
Full list of author information is available at the end of the article
© 2014 Froehner et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited.
Froehner et al. BMC Urology 2014, 14:28
http://www.biomedcentral.com/1471-2490/14/28
Page 2 of 8
Methods
uncertain preoperative PSA values were included in the
highest PSA risk groups.
Study sample
The study sample consisted of all 2205 patients who
underwent radical prostatectomy between December
1st, 1992 and December 31st, 2005 at our institution (a
university hospital). Approval by the institutional review
board of the University Hospital Dresden was obtained
(approval reference: EK 268092009). Seventy-four patients
with missing data on Gleason score, local tumor stage
or lymph node status were excluded thus leaving 2131
patients for analysis. Further demographic data is given
in Tables 1 and 2.
Investigated variables
Prostate-specific antigen (PSA), Gleason score, tumor stage,
Charlson score [6], American Society of Anesthesiologists
(ASA) physical status class [8], New York Heart Association
(NYHA) class of cardiac insufficiency [9], Canadian Cardiovascular Society (CCS) class of angina pectoris [10],
number of concomitant diseases (disease count), diabetes
mellitus, and body mass index were investigated as categorical variables. Age was treated as a continuous variable. Patients with neoadjuvant treatment and, therefore,
Data collection
Data was obtained from the patient records. The specimens of patients who underwent surgery prior to 1999
were reclassified in order to ascertain data uniformity. Perioperative cardiopulmonary risk assessment (ASA, NYHA,
CCS) classifications were derived from the anesthesiology
premedication records. In cases with obviously incorrect
classifications these were corrected under the surveillance
of a senior anesthesiologist before being entered into a
database.
The Charlson score was assigned based on the comorbidity data available in the database supplemented by
information derived from the discharge letters largely
following the original description of this comorbidity
index [6]. The presence of diabetes mellitus with or without end organ damage was recorded separately as another
comorbidity classification. Codes for each condition contributing to the Charlson score [6] were included in
the database. A disease count was calculated by adding
one point for any concomitant disease recorded in our
database (angina pectoris, hypertension, history of throm-
Table 1 The results of the univariate analyses using two-sided stratifications
Category
Events
Hazard ratio
PSA < 10 ng/mL
138/1165
1
PSA 10+ ng/mL or neoadjuvant therapy
163/966
1.18
Gleason score <8
198/1710
1
Gleason score 8-10
103/421
3.44
organ confined
168/1424
1
non confined
133/707
1.64
pN0
248/938
1
pN1
53/193
2.85
ASA 1-2
ASA 3
218/1774
1
83/357
2.88
Charlson score 0-1
220/1809
1
Charlson score 2+
81/322
3.18
NYHA 0-1
270/2002
1
NYHA 2+
31/129
1.91
CCS 0-1
268/2015
1
CCS 2+
33/116
2.85
Disease count 0-1
145/1296
1
Disease count 2+
156/835
1.97
No diabetes with end organ damage
276/2034
1
25/97
3.19
Diabetes with end organ damage
Body mass index <30 kg/m2
237/1775
1
Body mass index 30+ kg/m2
64/356
1.69
CI: confidence interval; p values are raw values.
95% CI
p
10-year survival
95% CI
87.3%
84.7-89.4%
83.5%
80.5-86.0%
0.93-1.48
0.1665
88.4%
86.4-90.1%
2.55-4.66
<0.0001
72.5%
66.7-77.4%
88.1%
85.9-90.0%
1.29-2.09
<0.0001
80.1%
76.3-83.3%
87.2%
85.2-88.9%
1.92-4.23
<0.0001
67.9%
59.2-75.1%
87.9%
85.9-89.6%
2.09-3.98
<0.0001
73.3%
67.2-78.4%
87.6%
85.7-89.4%
2.28-4.43
<0.0001
73.0%
66.7-78.3%
85.8%
83.8-87.6%
1.21-3.03
0.0059
79.2%
70.4-85.7%
86.4%
84.5-88.1%
1.74-4.67
<0.0001
71.2%
60.7-79.4%
89.1%
86.8-91.0%
1.55-2.49
<0.0001
79.7%
76.2-82.8%
86.2%
84.3-87.9%
1.78-5.71
0.0001
68.3%
55.2-78.3%
86.4%
84.4-88.3%
1.22-2.32
0.0014
80.4%
75.0-84.8%
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Table 2 The results of the univariate analyses using three-sided stratifications
Category
Events
Hazard ratio
138/1165
1
PSA 10–19.9 ng/mL
58/398
1.03
0.76-1.41
PSA 20+ ng/mL or neoadjuvant therapy
105/598
1.26
0.97-1.64
Gleason score <7
117/989
1
Gleason score 7
81/721
1.09
0.82-1.45
0.5600
Gleason score 8-10
103/421
3.19
2.35-4.34
<0.0001
organ confined, pN0
162/1380
1
non confined, pN0
86/558
1.30
0.99-1.70
pN1
53/193
3.14
2.09-4.72
PSA < 10 ng/mL
95% CI
p*
10-year survival
95% CI
87.3%
84.7-89.4%
0.8429
86.0%
81.4-89.5%
0.0852
81.9%
77.9-85.2%
88.8%
86.3-90.9%
87.7%
84.1-90.5%
72.5%
66.7-77.4%
88.3%
86.1-90.2%
0.0637
84.4%
80.4-87.7%
<0.0001
67.9%
59.2-75.1%
92.9%
88.0-95.9%
87.1%
84.9-89.0%
ASA 1
17/212
1
ASA 2
201/1561
1.83
1.27-2.65
0.0013
2.18-4.91
<0.0001
ASA 3
83/357
3.28
Charlson score 0
146/1323
1
Charlson score 1
74/486
1.53
1.13-2.08
Charlson score 2+
81/322
3.61
2.56-5.09
73.3%
67.2-78.4%
89.4%
87.3-91.2%
0.0057
82.8%
78.0-86.6%
<0.0001
73.0%
66.7-78.3%
86.4%
84.4-88.2%
77.0%
67.0-84.4%
NYHA 0
245/1877
1
NYHA 1
25/125
1.84
1.11-3.06
0.0181
1.26-3.22
0.0034
NYHA 2+
31/129
2.01
CCS 0
228/1804
1
79.2%
70.4-85.7%
87.2%
85.2-89.0%
CCS 1
40/211
1.65
1.12-2.45
CCS 2+
33/116
3.11
1.87-5.16
0.0123
79.5%
71.9-85.2%
<0.0001
71.2%
60.7-79.4%
Disease count 0
64/619
1
Disease count 1
81/677
1.25
0.90-1.73
0.1822
91.2%
88.2-93.4%
87.2%
83.6-90.0%
Disease count 2+
156/835
2.00
1.53-2.61
<0.0001
No diabetes
249/1877
1
79.7%
76.2-82.8%
86.7%
84.7-88.4%
Diabetes without end organ damage
27/157
1.47
0.93-2.32
0.0990
80.0%
70.5-86.6%
Diabetes with end organ damage
25/97
3.35
1.86-6.04
0.0001
68.3%
55.2-78.3%
Body mass index <30 kg/m2
Body mass index 30–34.9 kg/m2
2
Body mass index 35+ kg/m
237/1775
1
86.4%
84.4-88.3%
56/327
1.55
1.11-2.16
0.0094
81.4%
75.8-85.8%
8/29
6.90
2.10-22.68
0.0015
69.8%
46.1-84.7%
*versus lowest risk category; CI: confidence interval; p values are raw values.
bembolism, body mass index 30 kg/m2 or higher, history
of myocardial infarction, cardiac insufficiency, peripheral
vascular disease, cerebrovascular disease, lung disease, ulcer
disease, mild liver disease, diabetes mellitus, connective
tissue disease, hemiplegia, moderate or severe renal disease, solid tumors, leukemia, lymphoma, moderate or
severe liver disease, dementia, metastatic solid tumors).
This was done regardless of the severity of each condition
analogous to an approach described by Houterman and
co-workers [11]. Follow-up data were collected from
urologists and/or general practitioners, the patients,
relatives, health insurance companies, local authorities
or the local tumor register, whichever was necessary.
Thereby, only one patient was lost to follow-up. Causes
of death were assigned to the relevant categories by a
senior urologist (MF). Prostate cancer was considered
the cause of death in cases with uncontrolled disease
progression. Second cancers were considered the cause
of death when an uncontrolled second malignancy was
present at the time of death. Deaths in the absence of
uncontrolled prostate or second cancer were considered
from deaths from non-cancer competing (“comorbid”)
causes. Deaths from accidents or suicide were considered
a separate category. The cause of death was identified
reliably in all deceased patients.
Variables and stratifications
Comorbidity variables were included into the analysis
when they were available in our database and allowed for
a stratification by the degree of severity into 3 categories
Froehner et al. BMC Urology 2014, 14:28
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(none, mild or severe). Two- and three-sided stratifications were investigated for each variable. The stratifications used are shown in Tables 1 and 2. Commonly used
stratifications promising a maximal contrast for each
parameter were chosen in order not to miss potentially
relevant prognostic information.
Statistical analysis
Overall mortality was the primary study endpoint. KaplanMeier curves and Mantel-Haenszel hazard ratios were
calculated. Univariate comparisons were made with the
log rank test. Only parameters significantly associated
with mortality in univariate analysis were used for multivariate analysis. Cox proportional hazard models were
calculated to analyze combined effects of variables. Only
parameters that remained significantly associated with
mortality upon multivariable analysis were retained in
the final models. After stratification by body mass index
(<30 kg/m2 versus higher), the contribution of different
causes of death (prostate cancer: uncontrolled recurrent
disease, competing causes: all causes of death other than
uncontrolled recurrent prostate cancer, non-cancer competing causes: all non-cancer causes other than accidents
or suicide, second cancers: all cancer deaths other than
from uncontrolled recurrent prostate cancer) was determined by competing risk analysis [12]. The statistical
analyses were performed with the Statistical Analysis
Systems (SAS Institute, Cary, NC) statistical package.
Results
The mean age was 64.2 years. The mean follow-up in
the surviving patients was 9.2 years (median: 8.6 years;
interquartile range 4.3 years). Of the 2131 patients included in the analysis, 84 patients had died of prostate
cancer and 227 of competing causes up to now (maximum
follow-up: 19.4 years). The results of univariate analyses
are shown in Table 1 (two-sided stratifications) and Table 2
(three-sided stratifications) and the optimal Cox proportional hazard models for two-sided and three-sided
stratifications are shown in Table 3. In addition to patient
age, tumor stage and Gleason score, the Charlson score,
the ASA classification and the body mass index provided
complementary information on overall survival probability
in two-sided as well as in three-sided stratifications
(Table 3). Competing risk analysis showed that the
excess mortality in obese patients (body mass index of
30 mg/m2 or higher) was attributable to competing
mortality. This competing mortality was attributable to
non-cancer causes as well as second cancers (Figure 1).
There was no detectable association between obesity
and prostate cancer mortality (Figure 1). Considering
patients with and without one of the risk factors Charlson
score 2 or higher, the ASA class 3 or body mass index
Page 4 of 8
30 mg/m2 or higher, the observed survival difference
was somewhat higher in patients aged 65 years or older
(Figure 2). Stratifying patients by combining the three
comorbidity classifications with complementary prognostic information (weighing was done by adding one for
the risk classes ASA 2, Charlson score 1, body mass index
30 kg/m2 or higher and two points for the risk classes
ASA 3 or Charlson score 3 each patient) resulted in a wide
separation of the survival curves with a relatively balanced
distribution of the patients over the risk groups particularly when patients aged 65 years or older were considered
(Table 4).
Discussion
Overdiagnosis and overtreatment are crucial issues in
the management of early prostate cancer. Classifying
comorbidity could be a strategy to tackle this problem
[13]. However, so far, no consensus on the best way to
measure comorbidity in men with early prostate cancer
has been reached. Although the guideline of the European
Association of Urology mentions the ASA classification
beside the Charlson score is as a decision tool [14], to our
knowledge, a complementary information content of these
two classifications has not yet been demonstrated. Our
analysis showed that in men who are candidates for radical
prostatectomy the Charlson score, the ASA classification
and the body mass index measured different aspects of the
health status. Whereas the Charlson score is calculated as
a sum of several prognostically relevant diseases with different weights, the ASA classification evaluates the general
health status focused on the perioperative risk. Therefore,
the observed complementary information content of both
classifications (Table 3) was a plausible result. With the
exception of the body mass index, all other comorbidity
classifications used in our study were more or less
related either to the ASA classification or to the Charlson
score or both and for that reason did not provide significant complementary information despite a partially
strong association with survival in the univariate analysis
(Tables 1, 2 and 3).
The ability of a combination of prognostic tools to meaningfully stratify the relatively healthy candidates for radical
prostatectomy was clearly superior to that of all investigated
comorbidity assessment tools on their own. The combination of the tools resulted in higher survival differences,
more balanced distribution of the patients over the risk
groups and the consideration of different aspects of the
health status. There is currently no other comorbidity
classification that reaches overall survival differences
between the best and the worst risk group up to roughly
50% (Table 4) in this long-living population. Even in
the presence of serious comorbidity, the majority of men
selected for radical prostatectomy survive more than
10 years after surgery [15]. With the six risk groups, a
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Table 3 Multivariate analysis: optimal Cox proportional hazard models for two-sided and three-sided stratifications
Optimal model, 2-sided stratifications
Category
Age (per year)
Hazard ratio
95% confidence interval
p
1.06
1.04-1.08
<0.0001
Gleason score 8+
2.25
1.74-2.90
<0.0001
pN1
1.70
1.24-2.34
0.0010
ASA 3
1.58
1.17-2.12
0.0030
Charlson score 2+
1.71
1.27-2.30
0.0004
1.47
1.10-1.95
0.0080
2
Body mass index 30+ kg/m
Optimal model, 3-sided stratifications
Category
Hazard ratio
95% confidence interval
p
Age (per year)
1.06
1.03-1.08
<0.0001
Gleason score 7
1.07
0.80-1.43
0.6641
Gleason score 8+
2.21
1.63-3.00
<0.0001
ASA 2
1.84
1.10-3.07
0.0202
ASA 3
2.69
1.50-4.83
0.0009
Charlson score 1
1.24
0.93-1.66
0.1412
Charlson score 2+
1.79
1.29-2.47
0.0004
pT3-4 and pN0
1.07
0.81-1.42
0.6420
pN1
1.85
1.30-2.62
0.0006
Body mass index 30–34.9 kg/m2
1.37
1.02-1.84
0.0385
1.95
0.94-4.02
0.0718
2
Body mass index 35+ kg/m
Reference categories were other patients in the case of two-sided comparisons and the lowest risk category when two-sided comparisons were used.
relatively balanced distribution of patients, a dose–response
relationship, considerable survival differences (Table 4) and
easy applicability, this combined comorbidity assessment
tool could be useful both for risk stratification in clinical
trials and decision making. The combined comorbidity
index may be used to counsel candidates for radical prostatectomy with low risk tumors who consider deferred
curative treatment or to stratify patients enrolled into
clinical trials comparing different treatment options for
localized prostate cancer.
Obesity is associated with excess cardiovascular and cancer mortality [16-18]. In men with early prostate cancer,
however, conflicting data have been reported about the
prognostic significance of the body mass index [19,20]. In
our study, we found a significant association of obesity
(defined as a body mass index of 30 kg/m2 or higher)
with competing mortality but not with prostate cancer
mortality after radical prostatectomy (Figure 1). This
observation is supported by the relatively small contribution of prostate cancer to excess cancer mortality in obese
men compared with that of several other neoplasms
[17]. Thus, due to this association of obesity and excess
competing (but not prostate cancer) mortality, the body
mass index appears to be a suitable predictor of competing mortality complementary to the other comorbidity
measures in candidates for radical prostatectomy.
The vast majority of patients selected for radical prostatectomy belong to the low risk group in the Charlson
score (Charlson score 0: in our study 62%; elsewhere:
73% [4]) and to the intermediate risk group in the ASA
classification (ASA 2: in our study 73%; elsewhere: 65%
[21]). These imbalances limit the applicability of both
classifications on their own in clinical decision making.
In contrast, the combination of the Charlson score, the
ASA classification and the body mass index distributed
the patients in fairly balanced way over even more risk
groups (Table 4). Furthermore, the combination of a fairly
subjective assessment as the ASA classification with more
objective instruments as the Charlson score and the body
mass index compensates for the intrinsic weaknesses
of each classification, i. e. the lack of recording specific
comorbidities in the ASA classification and the disregard
of the personal impression of the patient’s health status
with the Charlson score and the body mass index. The
simultaneous recording of all three indicators may also
allow for a solution of the problem of retrospectively
determining the severity of health problems with chart
review and may compensate for errors in classification.
All three comorbidity measures are widely used and
easily applicable, even though the assignment of the
ASA class required a visit by a sufficiently experienced
anesthesiologist.
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Cumulative incidence
Cumulative incidence
A
B
Years
Years
Cumulative incidence
Cumulative incidence
C
D
Years
Years
Figure 1 Competing risk analysis of different causes of death stratified by the body mass index (green: body mass index lower than
30 kg/m2, red: body mass index 30 kg/m2 or higher), A: competing causes altogether (all causes other than prostate cancer), Pepe-Mori
test: p = 0.0196, B: non-cancer competing causes (all causes other than prostate or second cancers), Pepe-Mori test: p = 0.0411, C: second
cancers, Pepe-Mori test: p = 0.11, D: prostate cancer, Pepe-Mori test: p = 0.69.
Cumulative incidence
Cumulative incidence
A
B
15.4 %
4.7 %
Years
Years
No. at risk:
1052
1041
1016
848
584
373
189
97
1079
1061
1030
853
556
306
145
75
Figure 2 Cumulative incidence of overall mortality in patients without one of the risk factors ASA 3, Charlson score 2 or higher or body
mass index 30 kg/m2 or higher (green) versus those with one of these risk factors (red). A: patients younger than 65 years (n = 1052), hazard
ratio 3.66 (95% confidence interval 1.80-7.43, log rank test: p = 0.0003), B: patients aged 65 years or older (n = 1079): hazard ratio 4.27 (95% confidence
interval 2.65-6.86, log rank test: p < 0.0001).
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Table 4 Proportion of events, Mantel-Haenszel hazard ratios, 10-year overall survival rates, confidence intervals
and p values stratified by the score based on the three comorbidity classifications with complementary information
content ASA class, Charlson score and body mass index in the whole sample and subdivided into age groups
Age <65 years (n = 1052)
Points
Events
Hazard ratio
0
12/137
1
95% CI
p*
10-year survival
95% CI
91.5%
84.7-95.4%
1
47/450
1.44
0.81-2.56
0.2133
90.5%
86.7-93.3%
2
23/253
1.30
3
22/125
2.70
0.65-2.57
0.4582
90.9%
85.4-94.4%
1.35-5.39
0.0049
80.3%
69.6-87.6%
4
11/61
2.68
1.07-6.70
0.0346
82.5%
69.8-90.2%
5
6/26
7.11
1.73-29.24
0.0066
74.2%
47.2-88.8%
Points
Events
Hazard ratio
p*
10-year survival
95% CI
0
3/53
1
98.1%
87.4-99.7%
1
56/469
2.24
1.08-4.64
0.0300
88.0%
83.6-91.2%
2
46/259
2.60
1.32-5.13
0.0058
80.5%
73.5-85.8%
3
30/157
3.14
1.48-6.69
0.0030
78.2%
69.0-84.9%
4
29/106
4.07
1.98-8.37
0.0001
67.0%
54.7-76.6%
5
16/35
21.12
7.45-59.90
<0.0001
48.9%
26.2-68.3%
95% CI
p*
10-year survival
95% CI
93.4%
88.3-96.3%
0.0149
89.3%
86.5-91.5%
Age 65+ years (n = 1079)
95% CI
All patients (n = 2131)
Points
Events
Hazard ratio
0
15/190
1
1
103/919
1.73
1.11-2.69
2
69/512
2.00
1.26-3.18
0.0032
85.7%
81.4-89.0%
3
52/282
2.89
1.77-4.71
<0.0001
78.9%
72.2-84.2%
4
40/167
3.88
2.25-6.70
<0.0001
73.0%
64.2-80.0%
5
22/61
21.30
8.95-50.72
<0.0001
60.3%
43.2-73.7%
*versus lowest risk category; CI: confidence interval; p values are raw values.
This study has several limitations. Although the mean
follow-up was relatively long, only a small number of
patients died during follow-up. It is not entirely sure
that these patients are representative for the whole
sample. Furthermore, patient recruitment in our study
started about 20 years ago. Over that period of time,
diagnostic methods, classifications and the treatment of
concomitant diseases have changed and the life expectancy
might have increased. A complementary prognostic impact
of the ASA classification and the Charlson score has
already been demonstrated for patients with bladder
cancer [22,23], but not yet for patients with prostate
cancer. Therefore, a confirmation and validation of our
findings in different samples would be desirable. Given
a sufficient sample size and follow-up, such validation
would require limited effort because of the rapid accessibility of the ASA classification and the Charlson score
(as well as the body mass index) during retrospective chart
review. The survival rates observed in this study are
only valid for the population investigated (candidates for
radical prostatectomy) but not for different populations
(unselected patients or patients selected for other treatment options for localized prostate cancer.
Conclusion
The three easily applicable comorbidity classifications
Charlson score, ASA classification and body mass index
measure different prognostic aspects of the health status
in candidates for radical prostatectomy. Compared with
the use of one of these three classifications on its own,
the combination of the three instruments has several
advantages. The combined assessment provides a more
balanced distribution of patients over the risk groups,
stratification into more risk groups, a greater survival
difference between the best and worst risk groups and
a higher resistance to classification errors by employing
different and relatively independent aspects of the health
status.
Abbreviations
PSA: Prostate-specific antigen; ASA: American Society of Anesthesiologists;
NYHA: New York Heart Association; CCS: Canadian Cardiovascular Society;
SAS: Statistical Analysis Systems; BMI: Body mass index.
Froehner et al. BMC Urology 2014, 14:28
http://www.biomedcentral.com/1471-2490/14/28
Competing interests
The authors declare no conflicts of interest related to the matter discussed in
this manuscript.
Authors’ contributions
MF designed the study, collected and analysed data, wrote and drafted
the manuscript, AEK collected follow-up data, RK performed the statistical
analysis and drafted the manuscript, GBB contributed histopathological
data, OWH drafted the manuscript, MPW provided administrative support,
interpreted the data and drafted the manuscript. All authors read and
approved the final manuscript.
Authors’ information
MF is associate professor at the Department of Urology, AEK is medical student,
RK is retired professor at the Department of Medical Informatics and Biometry,
GBB is professor and chairman at the Department of Pathology of the Dresden
University of Technology, OWH is professor and chairman at the Department of
Urology of the University of Rostock, MPW is professor and chairman at the
Department of Urology of the Dresden University of Technology.
Acknowledgment
The authors thank Bernd Garbrecht, Gert Heine, Ulrich Klenk, Rainer Litz and
Caroline Menzel for their assistance in collecting clinical and follow-up data
for this study.
Author details
1
Departments of Urology, University Hospital “Carl Gustav Carus”, Technische
Universität Dresden, Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany.
2
Department of Medical Statistics and Biometry, University Hospital “Carl
Gustav Carus”, Technische Universität Dresden, Dresden, Fetscherstrasse 74,
D-01307 Dresden, Germany. 3Department of Pathology, University Hospital
“Carl Gustav Carus”, Technische Universität Dresden, Fetscherstrasse 74,
D-01307 Dresden, Germany. 4Department of Urology, University of Rostock,
Ernst-Heydemann-Strasse 6, D-18055 Rostock, Germany.
Received: 12 June 2013 Accepted: 18 March 2014
Published: 29 March 2014
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doi:10.1186/1471-2490-14-28
Cite this article as: Froehner et al.: A combined index to classify
prognostic comorbidity in candidates for radical prostatectomy. BMC
Urology 2014 14:28.