Obesity and radical prostatectomy margin rates: a comparison of open and minimally invasive surgery

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Background: Some investigators advise caution in performing minimally invasive prostatectomy in obese patients with prostate cancer due to high positive margin rates. We sought to determine if surgical modality in obese patients correlates with peri-operative outcomes, in particular margin positive rate.
Methods: We retrospectively analyzed our radical prostatectomy database to identify patients with a BMI ≥ 35 (Class II or III Obesity) who underwent open, laparoscopic, or robotic-assisted radical prostatectomy from 2004 to 2007 by 3 surgeons at our institution. Patients were categorized into two groups: open radical retropubic prostatectomy and minimally-invasive radical prostatectomy (MIS).
Results:
Of 1,157 patients who underwent prostatectomy, 123 patients (10.6%) had incomplete BMI information and were excluded. 94 patients (9.1%) had BMI >35 and were included.
BMI, age, PSA, and biopsy Gleason sum were similar between the open and MIS groups (Tables 1 and 2). Operative time, estimated blood loss (EBL), and length of hospital stay (LOS) were significantly higher in patients who underwent open surgery. Prostate size, pathologic Gleason sum and tumor stage were comparable.
The rate of positive surgical margins, which was ≥30% in both groups, was slightly higher in the MIS group. When compared to patients with BMI<35, the rate of positive surgical margin in the patients included in our study was 12% higher (p<0.01).
Conclusions: Patients with Class II or III obesity (BMI >35) have a high positive margin rate irrespective of surgical modality. This may be related to technical difficulties associated with operating on obese patients or to the presence of higher stage disease. Margin rates should not influence choice between open and minimally-invasive prostatectomy in obese patients. EBL, LOS and operative time all favor the laparoscopic or robotic approach.

Table 1.

	Open (n=30)	MIS (n=64)	P value
BMI	39.8 ± 7.7	38.6 ± 3.7	0.44
Age	58 ± 6	57 ± 6.1	0.70
PSA	5.4 ± 2.7	5.2 ± 3.4	0.84
Biopsy Gleason sum	6.4 ± 0.6	6.4 ± 0.7	0.87

Table 2.

	Open (n=30)	MIS (n=64)	P value
EBL (mL)	1046 ± 615	238 ± 126	<0.01
Operative time (min)	214 ± 44	171 ± 49	<0.01
LOS (nights)	3.4 ± 0.7	1.5 ± 1.3	<0.01
Prostate Size (g)	43 ± 18	51 ± 17	0.06
Pathologic Gleason Sum	6.6 ± 0.9	6.7 ± 0.9	0.59
Path Stage ≥ T3	8 (27%)	10 (16%)	0.27
Margin Rate	30%	31.3%	0.01

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