Predictors of positive surgical margins at open and robot-assisted laparoscopic radical prostatectomy: a single surgeon series
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- Weerakoon, M., Sengupta, S., Sethi, K. et al. J Robotic Surg (2012) 6: 311. doi:10.1007/s11701-011-0313-4
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Robot-assisted laparoscopic radical prostatectomy (RALRP), increasingly used to treat localized prostate cancer, has advantages over open radical prostatectomy (ORP) in terms of reduced bleeding and quicker convalescence. However, debate continues over whether RALRP provides superior or at least equivalent surgical outcomes. This study compares positive surgical margins (+SM), as a surrogate for long-term cancer control, at RALRP and ORP performed by a single experienced surgeon during the process of taking up RALRP. 400 consecutive patients undergoing surgery for prostate cancer under a single surgeon (DW) between November 1999 and July 2009 were studied. Prior to July 2005, all patients underwent ORP; after this date, most patients were treated by RALRP. Data were collected by retrospective chart review and analysed independently of the treating surgeon. +SM were defined as the presence of cancer at an inked surface. Overall, 23 (11.5%) of 200 patients undergoing RALRP had +SM, compared to 40 (20.0%) of 200 patients undergoing ORP (P < 0.05). On univariate logistic regression analysis, in addition to surgical approach (odds ratio [OR] = 1.92), patient age (OR = 1.05), pathologic stage (OR = 3.93) and specimen Gleason (GS) score (OR = 1.86) were significant predictors of +SM. On multivariate analysis, surgical approach, p-stage and specimen GS remained significant predictors of +SM. RALRP is associated with lower rates of +SM compared to ORP, even after adjusting for other known risk factors. Of note, the RALRP in this study were part of the surgeon’s learning curve.
KeywordsProstatectomy, robotic Prostatectomy, open Prostate cancer Positive surgical margins Risk factors Multivariate analysis
The daVinci robotic system is used to perform an increasing proportion of radical prostatectomies (RP) for the treatment of early stage prostate cancer (CaP). To date, robot-assisted laparoscopic RP (RALRP) has been clearly shown to have benefits over open RP (ORP) in terms of reduced bleeding and shorter hospital stay and convalescence [1, 2]. However, the principal surgical aims of RP are the so-called “trifecta” of cancer control, urinary continence and sexual potency. Opinion remains divided on whether RALRP provides superior or at least equivalent outcomes with respect to each of these three endpoints [1, 2].
The robust assessment of prostate cancer control requires long-term follow-up with accurate documentation of biochemical or clinical recurrence and death from CaP and other causes. However, in the short term, positive surgical margins (+SM) can be utilized as a surrogate for cancer control. Although it is well recognized that many patients with +SM remain recurrence-free in the long-term, +SM are an independent risk factor for subsequent recurrence, and can be viewed as a measure of oncological adequacy of RP . Published literature shows conflicting data relating to the risk of +SM at RALRP relative to ORP [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. The aim of this study was to examine the rate of +SM during RALRP and ORP as performed by a single experienced surgeon during the process of taking up RALRP.
Patients and methods
We studied 400 consecutive patients undergoing surgery for localized CaP under a single surgeon (who had performed in excess of 400 ORPs prior to the study period) between November 1999 and July 2009. Prior to July 2005, all patients underwent ORP; after this date, most patients were treated by RALRP. ORP was carried out using a standard approach with retrograde dissection of the prostate. RALRP was carried out trans-peritoneally, with antegrade dissection of the prostate. As previously described, a posterior approach was utilized to dissect the neuro-vascular bundles off the prostate and develop the “Veil of Aphrodite” during RALRP .
Data pertaining to patient demographics and pathologic details were collected by retrospective chart review, and analysed independently of the treating surgeon. Staging was according to the 2007 UICC-AJCC TNM staging system and grading according to the Gleason system. Percentage of positive cores (PPC) was defined as 100 × number of biopsy cores involved by prostate cancer/total number of biopsy cores obtained. +SM were defined as the presence of cancer at an inked surface of the specimen.
Data are expressed as median and range or mean and standard deviation, as appropriate. Comparisons between groups were undertaken using the chi-squared test for categorical variables and the Wilcoxon test for continuous variables. Logistic regression analysis was carried out, using univariate and multivariate models, to analyse the relationship between +SM and surgical approach as well as other risk variables. All statistical analyses were carried out using online calculators at http://www.statpages.org , and statistical significance was set at P < 0.05.
Clinical and pathologic characteristics of patients treated by open or robot-assisted laparoscopic radical prostatectomy
ORP (N = 200)
RALRP (N = 200)
Age (years), median (range)
PSA (μg/l), median (range)
Clinical stage, N (%)
Biopsy Gleason score, N (%)
3 + 4 = 7
4 + 3 = 7
Percent positive cores, N (%)
Prostate weight (g), median (range)
Specimen Gleason score, N (%)
3 + 4 = 7
4 + 3 = 7
Pathologic stage, N (%)
T2 or less
T3 or more
Univariate and multivariate logistic regression analysis of clinical variables predictive of positive surgical margins during open or robot-assisted laparoscopic radical prostatectomy
OR (95% CI)
OR (95% CI)
Percent +ve cores
Univariate and multivariate logistic regression analysis of pathologic variables predictive of positive surgical margins during open or robot-assisted laparoscopic radical prostatectomy
OR (95% CI)
OR (95% CI)
RALRP has become established as a surgical treatment for early CaP, although there is continuing debate over whether its outcomes are superior or at least equivalent compared to ORP. In this single surgeon series, we demonstrate that RALRP is associated with a lower risk of +SM compared to ORP, even after adjusting for accepted clinico-pathologic risk factors.
Interestingly, the pre-operative serum PSA and c-stage were found not to be associated with +SM, perhaps illustrating the limitations of PSA as a prognostic marker and the inaccuracy of clinical assessment of stage. Patient age at treatment was univariately but not multivariately associated with +SM, suggesting that the association was due to higher risk disease being treated in older patients. The PPC and bGS were also only univariately associated with +SM. However, the multivariate association of these two variables with +SM did approach statistical significance, suggesting that perhaps greater numbers may have provided sufficient power for this to be demonstrated. P-stage and sGS, both accepted risk factors for +SM, were strongly predictive of the risk of +SM in our study, on both univariate and multivariate analysis. Prostate size, which some studies have shown to be associated with a lower risk of +SM, had no influence on +SM in our study.
The above risk factors were found to differ somewhat between the RALRP and ORP groups in our study. Thus, the serum PSA was significantly lower among patients undergoing RALRP, and prostate size and p-stage both showed trends towards being lower. The distribution of sGS was also different, with fewer patients with Gleason 6 disease but more with Gleason 7 disease in the RALRP group. In part, these differences may be attributable to selection of patients with larger prostates or more adverse clinical features for ORP during the very early stages of taking up RALRP. However, beyond the initial 50 cases or so, patients have been considered for RALRP irrespective of these features, with ORP carried out only on the basis of patient preference. An additional factor that may also have contributed to these differences is a continuing process of stage migration, since on average the ORP patients were treated at a slightly earlier period. However, being consecutive cases, the difference in time was short.
In any event, even accounting for the differences in risk profile between the RALRP and ORP groups, on multivariate analysis the surgical approach still accounted for an almost two-fold difference in the risk of +SM in favour of RALRP in our study. Considering clinical variables, only the surgical approach remained a significant predictor of +SM, with PPC and bGS both approaching, but not achieving statistical significance. Among pathologic variables, p-stage and sGS were significant predictors of +SM, but even after adjusting for these factors, surgical approach also retained a significant association with +SM. Notably, on stratified analysis, for any particular stage or Gleason score, RALRP was associated with a lower rate of +SM compared to ORP.
Published studies comparing positive surgical margins at open radical prostatectomy (ORP) and robot-assisted laparoscopic radical prostatectomy (RALRP)
OR (95% CI)
Factors adjusted for
St. Vincents Sydney 
Mayo Clinic 
U Wis 
Johns Hopkins 
Age, race, biopsy Gleason score, PSA, c-stage, number of cases performed
Epworth Richmond 
Age, PSA, p-stage
Age, PSA, year of surgery, BMI, c-stage, biopsy Gleason score
Metro Health Michigan 
Age, PSA, year of surgery, c-stage, biopsy Gleason score, BMI, nerve sparing
Clearly, RALRP can be associated with lower +SM compared to ORP, but not necessarily so. RALRP affords the surgeon technologic advances including magnified binocular vision and wristed instrumentation, which are cited as factors important in reducing +SM. We believe that, in addition to these technologic advances, our approach during RALRP to the posterior dissection of the prostate and development of the plane between the prostatic capsule and neurovascular bundle is an important factor in reducing +SM in our series . We find that the antegrade dissection of the prostate, as well as the optical and physical features of the daVinci robot, allow this portion of RP to be carried out under vision and to be tailored appropriately to the risk features of the patient’s disease. Thus, we routinely carry out nerve-sparing during RALRP for all patients, but with the extent of nerve sparing guided by a pre-operative assessment of the patient’s risk features.
As every practicing surgeon would realize, the daVinci robotic system is but a surgical instrument, and like any other requires appropriate surgical expertise to obtain optimum results. Studies have clearly shown the relationship of surgeon experience and volume to outcomes at RP, thus highlighting the importance of the surgeon in such analyses. It is our belief that, at least in part, the conflicting literature on +SM with various approaches to RP is a result of comparing outcomes from surgeons with disparate levels of expertise. The most appropriate comparison therefore is between the results obtained by a single surgeon using different approaches. It is to be noted that one of the strengths of our study is that it compares results from cases performed by a single surgeon. In particular, while the RALRP cases included his learning curve, the ORPs were part of a mature series from an experienced surgeon who had already performed hundreds of cases. The fact that consecutive cases were studied, and the most recent ORPs were undertaken in parallel with the RALRPs, hopefully minimizes any impact that temporal trends may have on disease characteristics, surgical technique or pathologic analysis.
RALRP is associated with a lower rate of +SM compared to ORP, even after adjusting for known clinical and pathologic risk factors.
Conflict of interest