Table
1 summarises the relationship between BNP in radical prostatectomy and positive surgical margins in the studies reviewed. Katz et al. reported data on a prospective series of 235 patients who underwent LRP between 1998 and 2001. During 2000, they stopped preserving bladder neck, and they found that by 2001, the rate of PSM at bladder neck fell from 9.75 to 0% [
16]. Their series, however, was consecutive rather than randomised and possible bias related to the increasing experience of the surgeon cannot be excluded. Similarly, Srougi et al. in their RCT found that bladder neck margins were positive for tumour in 6 of 70 patients, including 4 from the BNP group and 2 from the non-BNP group. Although the difference between groups in the rate of positive bladder neck margins was not statistically significant (
p = 0.40), margins were positive at the bladder neck alone in 3 of the 31 (10%) patients from the BNP group and in none of the 39 from the non-BNP group (
p = 0.08). This data raised ethical concerns and prompted the investigators to halt the study early [
14].
Table 1
Systematised data
Gomez | 1993 | 50 | Prospective | ORP | 18 (36%) | 3 (6%); 0 only BN | – | n/a |
Licht | 1994 | 206 (114/83) | Prospective | ORP | – | 9 (7.9%); 0 only BN | 5 (6%); 0 only BN | 0.61 |
Shelfo | 1998 | 365 | Retrospective | ORP | 119 (33%) | 27 (7%); 2 (0.5%) only BN | – | n/a |
Freire | 2009 | 619 (348/271) | Prospective | RARP | 79 (12.8%) | 5 (1.4%) | 6 (2.2%) | 0.45 |
Srougi | 2001 | 69 (31/38) | RCT | ORP | – | 4 (13%); 3 (10%) only BN | 2 (5%); 0 only BN | 0.24 0.047 |
Katz | 2003 | 235 | Prospective | LRP | 62 (26.3%) | 9.75% | 0 | n/a |
Bianco | 2003 | 555 | Prospective | ORP | 178 (32%) | 13 (2%); 2 (0.4%) only BN | – | n/a |
Selli | 2004 | 131 | Retrospective | ORP | 30 (22%) | 7 (5%) only BN | – | n/a |
Stolzenburg | 2010 | 240 (150/90) | Retrospective | LRP | 25 (10.4%) | 1 (0.7%) only BN | 1 (1%) only BN | 0.802 |
Chlosta | 2012 | 194 | Prospective | LRP | 14 (7%) | 0 | – | n/a |
Nyarangi | 2012 | 208 (95/104) | RCT | RARP/ORP | 28 (13.5%) | 2 (2%) only BN | 0 | 0.15 |
Friedlander | 2012 | 1067 (791/276) | Prospective | RARP | 147 (13.8%) | 9 (1.1%) | 7 (2.5%) | 0.094 |
Golabek | 2014 | 295 | Retrospective | LRP | 86 (29.15%) | 14 (16.3%); 2 (2.3%) only BN | – | n/a |
Brunocilla | 2014 | 80 (40/40) | Prospective | ORP | 13 (16%) | 0 | 0 | 1 |
Lee | 2014 | 599 (581/18) | Retrospective | RARP | 105 (17.5%) | 8 (1.4%) | 0 | 0.61 |
| Mean bPSM | 4.89% | 1.86% | |
Median bPSM | 2% | 1% |
Other authors, however, did not confirm these findings and reported that BNP technique did not negatively correlate with PSM. Gomez et al. performed a prospective study on 50 patients undergoing BNP open radical prostatectomy. In their series, the overall rate of PSM was 36%, but the bladder neck was involved only in 3 patients (6%) and all of these had PSM elsewhere indicating that these might simply have been difficult cases with widespread extensive disease. The high rate of positive margins in this study is almost certainly related to the high rate of T3 disease (25%) [
39]. Similar findings were described by Licht et al. in a prospective cohort of 206 patients. Base PSM rate was 7.9% in the BNP group, but in no patients was it the only positive site. Bladder neck involvement was also associated with higher stage, more than 50% likelihood of seminal vesical involvement and a higher incidence of lymph node metastases [
30]. Moreover, in their retrospective series of 365 patients treated with RRP and BNP, Shelfo et al. reported an overall and base PSM rates of 33 and 7%, respectively. The bladder neck was the only site involved in two (0.5%) of the cases [
11]. A larger prospective study of 555 men undergoing RRP with BNP technique was performed by Bianco et al. and confirmed those findings. They reported a total PSM rate of 32%; however, PSM at bladder neck were found in 13 patients (2%) and it was the only location in only two patients (0.4%) [
36]. In a prospective study by Freire et al. on 619 men undergoing RARP, the total and base PSM recorded were 12.8 and 1.4% in BNP group and 2.2% in non-BNP group, respectively [
42]. A large prospective study by Friedlander et al. on 1067 patients reported the same overall PSM in BNP and non-BNP patients (13.8%), base-positive margins being 1.1 and 2.5%, respectively [
9]. A prospective, randomised, single-blind trial was performed by the group of Nyarangi et al. in 208 patients undergoing RARP with or without BNP. They found no evidence of a difference in surgical margin status between the control and the bladder neck preservation group (12.5 versus 14.7%,
p = 0.65). Only 2% of men presented an isolated base PSM [
41]. Chlosta et al., in a prospective series of 194 patients undergoing BNP LRP, assessed a total PSM of 7%, none of them was located at the bladder neck [
37].Similarly, Brunocilla et al. described an overall PSM rate of 16% and no PSM at the prostate base both in men underwent BNP and non-BNP RRP [
10]. Golabek et al., in a retrospective study of 295 men undergoing BNP laparoscopic radical prostatectomy, found a total PSM rate of 29.15%. The distribution of PSM for pT2, pT3 and pT4a was 15.3 (27/176), 49.1 (58/118) and 100% (1/1), respectively. Overall, 20.0% had an isolated PSM and 13.7% had multiple positive sites. The bladder neck was a positive margin in 14 cases (16.3%), and in 12 out of those (85.7%), it was in combination with a PSM at one or two other sites [
11].The relatively high incidence of PSM in this study could be attributed to a large number of extracapsular tumours (40.3%). Furthermore, as BNP was performed consistently, patients with median lobe hypertrophy or high-risk features were not excluded. Selli et al. reported an overall PSM rate of 22% in 131 men undergoing RRP with BNP technique. In this series, only seven cases (5%) were positive exclusively at the bladder neck and this subgroup included patients with more aggressive pT3a disease, two of whom also had lymph node involvement, two received 3 months of neoadjuvant androgen deprivation therapy and five presented a Gleason score > 7 [
13].
The incidence of positive surgical margins described in literature is equivalent among open, laparoscopic and robotic approaches. Tewari et al. reported an overall PSM rates of 24.2% for ORP, 20.4% for LRP and 16.2% for robot-assisted laparoscopic prostatectomy (RALP; no statistical evidence of a difference). Furthermore, pT2 PSM rates were 16.6% in ORP, 13.0% in LRP and 10.7% in RALP, whereas pT3 PSM rates were 42.6% in ORP, 39.7% in LRP and 37.2% in RALP [
43]. Similarly, Novara et al. reported a 15% mean rate of PSMs in RARP series with a stage-specific rate of 9% for pT2 (4–23%), 37% for pT3 (29–50%) and 50% for pT4 (40–75%), supporting the evidence that a higher stage confers a higher risk of positive surgical margins. The prevalence of PSM stratified by location was as follows: apex 5% (1–7%), anterior 0.6% (0.2–2%), bladder neck 1.6% (1–2%) and posterolateral 2.6% (2–21%). Multifocal PSM was detected in 2.2% (2–9%) of the cases [
44]. As expected, most of the studies included here report a higher risk of positive surgical margins for tumours of higher grade and stage and higher PSA values [
9,
11,
12,
16,
30,
36,
39].
Other clinical factors that may increase the risk of PSM include elevated BMI, large prostate, previous prostatic or abdominal surgery [
31,
45,
46]. These factors are still the object of investigation in the current literature, while the surgeon experience has been more clearly linked to improved outcomes. The incidence of PSM is relatively high at the beginning of the learning curve, but it tends to reach a plateau with increasing experience. The number of procedures estimated to reduce the positive margin rate to a minimum is reported in literature with a range of 200–250 cases in laparoscopic series. As regards robotic surgery, a single-surgeon study by Thompson et al. [
47] reported a plateau after 100–200 RARP in pT2 disease and after 200–300 cases in pT3 disease, and the randomised controlled trial of open versus robotic surgery suggested a plateau between 100 and 200 cases [
48,
49]. However, a multicentre review of 3794 patients described a learning curve with a plateau for PSM in pT3 that was only reached after 1000 cases [
50‐
52].