Increasing Body Mass Index Negatively Impacts
Outcomes Following Robotic Radical Prostatectomy
Michael P. Herman, MD, Jay D. Raman, MD, Steven Dong, MD,
David Samadi, MD, Douglas S. Scherr, MD
(BMI) on outcomes following robotic radical prostatectomy.
Methods: From January 2003 to May 2005, 132 patients
with clinically localized prostate cancer underwent a ro-
botic radical prostatectomy. Patients were divided into 3
cohorts based on BMI: 38 normal (range, 18 to 24.9), 60
overweight (range, 25 to 29.9), and 34 obese (BMI?30).
Results: The operative time was significantly longer in
obese (304 min) men compared with overweight (235
min) and normal (238 min) BMI patients (P?0.001). Esti-
mated blood loss was significantly greater in both the
obese (316 mL) and overweight (318 mL) groups com-
pared with men with normal BMI (234 mL) (P?0.005).
Three patients (1 obese and 2 overweight) required con-
version to open surgery. Twenty-three of 132 men (17%)
had a positive surgical margin, with obese (21%) and
overweight (20%) men at a greater risk compared with
normal BMI men (11%). No significant differences existed
between groups with regard to final pathologic stage,
Gleason score, biochemical recurrence at 1-year, and
postoperative complication rate.
Conclusion: Overweight and obese men had a longer op-
erative duration, greater blood loss, longer hospital duration,
and higher positive surgical margin rate. Robotic prostatec-
tomy in men with elevated BMI is technically more challeng-
ing and is associated with more operative morbidity.
Key Words: Body mass index, BMI, Prostate cancer,
Robotic prostatectomy, Urologic oncology.
Over 70% of men over age 40 are obese or overweight,
with current trends suggesting that these numbers will
only increase with time.1Numerous studies suggest that
body mass index (BMI) plays an important role in the
natural history of prostate cancer. Obesity has been
associated with an increased risk of aggressive disease
and death from prostate cancer.2,3Several studies have
further demonstrated that BMI correlates with an in-
creased risk of biochemical failure after radical prosta-
tectomy.4–6Although this may be attributable to aggres-
sive cancer biology, it is also possible that operative
considerations contribute to these poorer outcomes.
Several groups have previously demonstrated that in-
creasing BMI correlates with a higher likelihood of
positive surgical margins and capsular incision in both
open and minimally invasive radical prostatectomies.4,7
Given the increasing incidence of overweight and
obese men, it is imperative to understand the impact of
BMI on surgical outcomes for prostate cancer.
Minimally invasive surgery offers several advantages
compared with traditional open methods, including de-
creased blood loss, less perioperative pain, and anal-
gesic requirements, shorter hospital stays, faster conva-
lescence and return to work, and improved cosmesis.
Robotic radical prostatectomy is becoming a well-ac-
cepted component of prostate cancer therapy.8,9How-
ever, the impact of BMI on surgical outcomes in robotic
radical prostatectomy has not been well defined. Two
recent studies have attempted to characterize this effect
with somewhat conflicting results.10,11While Ahlering
and colleagues11found that obese men had significantly
more complications than men with normal BMI did,
Mikhail et al12noted no difference in peri-operative
morbidity despite an increased operative time and
Here then, we attempt to clarify the impact of BMI on
operative outcomes from robotic radical prostatectomy by
describing our single institution experience with 132 con-
secutive patients, 71% of whom were overweight or
Department of Urology, The New York-Presbyterian Hospital, Weill Medical Col-
lege of Cornell University, New York, New York, USA (Drs Herman, Raman, Dong).
Department of Urology, Columbia University College of Physicians and Surgeons,
New York, New York (Dr Samadi).
Department of Urology, New York-Presbyterian Hospital - Weill Cornell Medical
Center, New York, New York (Dr Raman).
Address reprint requests to: Jay D. Raman, MD, Department of Urology, University
of Texas–Southwestern Medical Center, 5323 Harry Hines Blvd, J8.106, Dallas, TX
75390-9110, USA. Telephone: 214 648 2225, Fax: 214 648 7876, Email:
© 2007 by JSLS, Journal of the Society of Laparoendoscopic Surgeons. Published by
the Society of Laparoendoscopic Surgeons, Inc.
Between January 2003 and May 2005, 132 consecutive pa-
tients with clinically localized prostate cancer underwent a
robotic radical prostatectomy performed by 2 surgeons (DSS
and DS) at the New York-Presbyterian Hospital. All patients
had biopsy proven adenocarcinoma of the prostate and
were staged according to the 2002 American Joint Commit-
tee on Cancer (AJCC) classification. BMI was calculated as
weight in kilograms divided by height in meters squared.
Patients were categorized into 3 groups based on preoper-
ative BMI: normal (BMI 18 to 24.9), overweight (BMI 25 to
29.9), and obese (BMI?30).
All patients underwent a robotic radical prostatectomy using
the da Vinci surgical system (Intuitive Surgical Inc., Sunny-
vale, CA). The procedure was performed as described by
Menon et al8with a few minor modifications.9Briefly, to
optimize nerve sparing, all prostatic pedicles were clipped
and sharply divided without using electrocautery. Judicious
use of intraoperative frozen sections was utilized to help
decrease the incidence of positive surgical margins. A bilat-
eral pelvic lymph node dissection was performed following
completion of the urethrovesical anastomosis in patients
with a greater than 2% chance of positive lymph nodes as
obtained from the Partin predictive tables.
Patients were seen approximately one week postopera-
tively for catheter removal. Cystograms were not routinely
obtained before catheter removal. Postoperative PSA val-
ues were evaluated 6 weeks postoperatively, every 3
months for the first year, every 6 months for the second
year, and yearly thereafter.
Outcomes and Statistical Analysis
Prospectively collected data included patient age, clinical T
stage, biopsy Gleason score, and PSA. Operative outcomes
studied included operative time, estimated blood loss (EBL),
and nerve sparing. Postoperative outcomes were length of
hospital stay, interval to catheter removal, pathology, margin
status, complications, and PSA recurrence. Excel 2000 (Mi-
crosoft, Redmond, Washington) software and SAS for Win-
dows, version 9.1 (SAS Institute, Cary, North Carolina) were
used to perform all statistical calculations with P?0.05 con-
sidered statistically significant. The chi-square (?2) log-rank
test with the Yates correction factor and the unpaired,
2-tailed Student t test were used to compare variables be-
tween normal, overweight, and obese men.
Table 1 outlines the preoperative data on the study patients.
Of the 132 men, 38 (29%) had normal BMI, 60 (45%) were
overweight, and 34 (26%) were obese. These percentages
reflect the relative BMI distribution seen in the general pop-
data between the groups regarding age, baseline PSA, or
biopsy Gleason score. Obese patients were noted to have a
higher percentage of clinical T1c cancers compared with
overweight and normal BMI patients.
The operative parameters are shown in Table 2. The
mean operative duration for obese patients was signifi-
NormalOverweight ObeseMeanP Value
Number of Patients
Preop PSA (range)
Clinical Stage (%)
Biopsy Gleason Score (range)
*Obese patients had a significantly higher percentage of clinical T1c cancers and lower percentage of T2 cancers compared with
overweight and normal patients.
cantly longer than that for normal and overweight men
(304 vs 238 and 235 minutes, respectively) (P?0.001). The
estimated blood loss was also significantly higher in over-
weight and obese men compared with that in men with
normal BMIs. Of the 132 robotic prostatectomies, bilateral
nerve sparing was performed in 90% of the cases. No
significant difference existed between the groups, al-
though there was a trend towards decreased bilateral
nerve sparing as BMI increased (94% vs 90% vs 82%).
Three cases required conversion to open prostatectomy;
one in the obese group secondary to a large intravesical
median lobe and 2 in the overweight group for bleeding
and dense adherence to the rectum. None of the patients
with a normal BMI required conversion to open surgery.
The pathologic features and postoperative data are shown
in Table 3. No significant difference existed in Gleason
sum score or pathologic stage among the various cohorts.
There was a trend, however, towards fewer capsule-con-
fined (T2) tumors in the overweight and obese groups
(P?0.13). Further, normal BMI patients had fewer positive
surgical margins (11%) when compared with the over-
weight (20%) and obese (21%) patients. Normal BMI pa-
tients also had a shorter hospitalization than did the over-
weight and obese men, but there were no differences in
duration to Foley removal (data not shown) or postoper-
ative complications. Eight of 132 (6%) patients had a
complication, with 3 being major (2 anastomotic leaks and
1 postoperative bleed requiring transfusions). At a short
interval follow-up of 1-year, no difference was found in
biochemical recurrence rates between the groups.
At 1-year follow-up, 95% (126/132) of men were fully
continent without the requirement of any pads. Our early
data noted no difference in continence rates between the
3 groups (normal 96%, overweight 94%, and obese 92%).
Normal OverweightObese OverallP Value
OR Duration* (min) (range)
Bilateral nerve sparing (%)
Open conversion (%)
*Obese patients had a significantly longer operative duration when compared to normal and overweight patients.
†Normal body mass index (BMI) patients had a significantly lower estimated blood loss (EBL) than overweight or obese patients.
Pathologic and Postoperative Data
Pathologic Stage (%) NormalOverweightObese OverallP Value
Pathology Gleason Score
Positive Margins (%)
Hospital Stay (days)*
Undetectable PSA (%)†
*Normal BMI patients had a significantly shorter hospitalization than did overweight or obese patients.
†1-year post robotic prostatectomy.
‡Normal BMI (3): bladder neck contracture, hematuria, lower extremity paresthesia; overweight (3): anastomotic leak, postoperative
bleed, urinary retention; obese (2): anastomotic leak; fever.
Increasing Body Mass Index Negatively Impacts Outcomes Following Robotic Radical Prostatectomy, Herman MP et al.
Although we did note a trend towards better bilateral
nerve sparing in the normal BMI group, we are waiting for
the data to fully mature before attempting to report a more
Obesity is one of the most pressing issues facing the US
healthcare system. Beyond its known associations with
diabetes, coronary artery disease, and hypertension, obe-
sity also has a significant impact on mortality in cancer
patients.2With over 70% of US men over age 40 over-
weight and obese, urologists will have to deal with the
ramifications of this epidemic.1In particular, prostate can-
cer is one disease in which elevated BMI likely plays a
significant role. Although there have been some conflict-
ing studies, obesity appears to correlate with higher grade
and more aggressive disease, as well as an increased
likelihood of death from prostate cancer.2,4,13–17
Elevated BMI has been associated with biochemical fail-
ure after radical prostatectomy. Whether this is due to
aggressive disease biology or to technical limitations is not
fully clear. Freedland and colleagues7attempted to deter-
mine whether the increased rate of biochemical failure in
obese patients was due to technically inferior surgery.
Using capsular incision on the pathological specimen as a
proxy for a worse technical operation, they found that
mildly obese patients had a 30% increased chance of
capsular incision and moderately to severely obese men
had a 57% increased risk. Several other studies have fur-
ther noted a trend towards increased positive surgical
margins in the overweight and obese patients.4,5Interest-
ingly, however, in a study of postprostatectomy patients
with negative surgical margins, the SEARCH database
study group still found an increased risk of biochemical
failure in patients with elevated BMI.14This observation
led to the conclusion that a technically inferior operation
cannot fully account for the outcome differences.
Robotic radical prostatectomy has been shown to be a
reasonable and effective treatment modality for prostate
cancer.8–10However, the impact of BMI on the effective-
ness of this surgical procedure has yet to be fully eluci-
dated. To date, there are only 2 studies that have investi-
gated surgical outcomes of robotic prostatectomy in
overweight and obese men compared with men with
normal BMI.11,12We add to this literature by contributing
our experience with a large series of patients from a single
academic institution. Similar to the 2 prior studies, we
failed to note any statistical difference in age, baseline
PSA, clinical T stage, or biopsy Gleason score among our
cohorts. Of note, the disease characteristics of patients in
all of these studies may reflect a selection bias towards
men who are surgically fit for an operative procedure. We
acknowledge that our study, as well as others, may there-
fore be selecting the “healthiest” of the heavy patients.
Our series demonstrated that obese men had a signifi-
cantly longer operative duration (by almost 60 minutes)
compared with overweight and normal BMI men. It is
likely that this prolonged operative time is at least partly
related to the increased blood loss seen in obese men in
all 3 studies. Other factors that may contribute to this
increased surgical time include suboptimal port place-
ment, robotic arm positioning, dissection of fat planes,
In addition to the prolonged operative time and increased
blood loss, trends towards decreased bilateral nerve spar-
ing, increased open conversions, and longer hospitaliza-
tion in overweight and obese patients all point to a tech-
nically more challenging operation. Despite this, there
was no difference in complication rates between the co-
horts suggesting that even with a technically more chal-
lenging operation, overweight and obese patients were
not at increased risk from the surgery itself.
Beyond the perioperative variables discussed above, on-
cologic control is of paramount importance. Our data
noted no difference in biochemical recurrence rates be-
tween the 3 groups at relatively short 1-year follow-up.
Although the ultimate measure of an intervention is the
ability to prolong long-term survival, surgical technique
can be assessed in the short-term by analyzing pertinent
oncological variables such as pathologic margin status. It
is generally agreed that a positive margin is indicative of
incomplete tumor resection and bears significant prognos-
tic importance. Several institutions have demonstrated the
independent prognostic significance of positive surgical
margins across all stages of disease.18In our series, there
was a trend towards increased positive surgical margins
between normal (11%), overweight (20%), and obese
(21%) men. While this could reflect the inherent technical
difficulties of operating on heavy patients, it may also be
due to the advanced disease noted among men with
elevated BMI. Indeed, in our series, the obese and over-
weight patients had an increased incidence of pT3 cancers
than did normal BMI men (15% and 18% vs 8%, respec-
tively). This increase in locally advanced disease, though
not significant, further confirms observations in the liter-
ature that these men are at increased risk of aggressive
cancer. Future studies with larger cohorts of patients that
control for pathologic stage will be needed to explore the
causative factor behind the increased positive surgical
Finally, postoperative quality of life is an important con-
sideration when counseling patients. Our preliminary data
(not shown) suggests that potency and continence rates
are similar among the study groups. Interestingly, we did
note a trend towards better bilateral nerve sparing in
patients in the normal BMI group. This may eventually
translate into better erectile function, though longer-term
data are needed. Clearly, both issues require further in-
vestigation with patient-based validated questionnaires,
and we are waiting for our data to mature before com-
menting more definitively. Indeed, spontaneous improve-
ments in continence and potency continue up to 2 years
following radical prostatectomy, thus emphasizing the
evolving nature of these variables.19,20
Compared with men with normal BMIs, overweight and
obese patients had a longer operative time, greater blood
loss, increased probability of open conversion, higher
positive surgical margin rate, and a longer hospitalization.
While robotic radical prostatectomy is an acceptable treat-
ment modality for men with elevated BMI, it is technically
more challenging and is associated with more operative
morbidity. Future studies will need to assess the impact of
increasing BMI on long-term prostate cancer outcomes,
continence, and potency.
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Increasing Body Mass Index Negatively Impacts Outcomes Following Robotic Radical Prostatectomy, Herman MP et al.