Introduction

Benign prostatic hyperplasia (BPH) adversely affects the quality of life in men throughout the world. An estimated 1.1 billion men suffer from BPH and its associated symptoms. [1] The proliferation of prostatic smooth muscle and epithelial cells can lead to lower urinary tract symptoms (LUTS), which include storage and voiding symptoms such as nocturia, urgency, daytime frequency, and sensation of incomplete emptying. Because of the increasing prevalence of these symptoms in the aging population due to BPH, the American Urological Association (AUA) has guidelines for both medical and recently updated surgical management of BPH. [2, 3••]

Medical management of BPH primarily revolves around alpha-blockers and 5α-reductase inhibitors, whether it be single-drug therapy or the combination. [2] Clinicians should consider surgical intervention when patients complain of moderate-to-severe LUTS not sufficiently treated by medication or any BPH-related structural changes in the urinary system. Recommendations for surgery, as stated by the AUA guidelines, include renal insufficiency, refractory urinary retention, recurrent urinary tract infections (UTIs), recurrent bladder stones or gross hematuria, and/or LUTS refractory to medical therapies. [3••]

Recent advancements in minimally invasive approaches for prostate surgery have provided numerous options for surgical intervention. Prostate size is typically the determinant factor for the type of treatment patients receive. [3••] Transurethral resection of the prostate (TURP) remains the historical standard for comparison of treatments for BPH and is recommended for small and average size glands. Surgeons versed in bipolar TURP have shown excellent results in prostates > 60 grams (g). Newer laser therapies such as holmium laser enucleation of the prostate (HoLEP) or thulium laser enucleation of the prostate (ThuLEP) are now considered prostate size-independent options. However, not all providers have access to or are sufficiently trained in these modalities. Therefore, simple prostatectomy is still a proven and recommended option in patients with large glands. The classic minimal size to recommend a simple prostatectomy has been > 80 g [2]; however, the updated AUA guidelines no longer recommend a specific size cutoff for large glands as large is a relative term. [3••]

The open approach to simple prostatectomy (OSP) has classically been regarded as the standard of care for large glands due to the beneficial long-term functional outcomes after surgery and greater volume of adenoma removed. [2, 4, 5] However, because OSP is often cited to have higher estimated blood loss (EBL), higher rates of transfusions, and longer length of stay (LOS), minimally invasive prostatectomy has increasingly been pursued, and notably, OSP cases have been decreasing as reflected by national trends. [6, 7] Laparoscopic simple prostatectomy (LSP) is considered equivalent to OSP in terms of functional outcomes [8, 9], but a purely laparoscopic approach is considered technically difficult and the steep learning curve has prevented wider acceptance among urologists. [10] On the other hand, robot-assisted simple prostatectomy (RASP) has become a common substitution for OSP in urologic patients due to the routine use of robot-assisted surgery for radical prostatectomy. The increased comfort of urologic surgeons in performing robot-assisted prostate surgery coupled with the decreased transfusion rates in RASP, makes the transition to robotic surgery the expected next step in treating large volume BPH [11•].

The previous AUA guidelines on management of BPH published in 2011 considered RASP as investigational owing to the relative lack of evidence supporting this surgical approach. [2] The updated surgical management guidelines recently published in 2018 now recommend all approaches (open, laparoscopic, and robotic) to simple prostatectomy, depending on the surgeon’s expertise with the technique. [3••] Hence, there is no longer a true single gold standard to managing bothersome LUTS in large glands. However, the guidelines do not go into further details on comparing the techniques, specifically the robotic compared to the open approach. The goal of this report is to provide a review of the literature on both RASP and OSP so that their functional peri- and post-operative outcomes may be compared. While there are certainly other effective minimally invasive treatments for large glands such as HoLEP that have been directly compared to RASP [12, 13], our intent was to narrow the focus to simple prostatectomy in this era of expansion of robotic surgery.

Comparison of Surgical Approaches

Open simple prostatectomy is classically performed by either the retropubic or suprapubic approach. The suprapubic prostatectomy, described by Eugene Fuller in 1894 and popularized by Peter Freyer in 1900, is performed either by a vesicocapsular incision (Freyer’s procedure) or only with a longitudinal bladder incision (modified Freyer’s procedure). [14] Direct vision of the bladder and bladder neck are afforded by this approach but the prostatic apex is difficult to visualize. The retropubic OSP described in 1945 is performed by a transverse capsular incision referred to as the Millin procedure and avoids entering the bladder. [15] While this technique has the advantage of better control of bleeding and visualization of adenoma, concomitant bladder lithiasis or diverticula cannot be addressed.

Robotic simple prostatectomy can also be classified as either involving a transcapsular or transvesical approach. The first technical description of RASP was published by Sotelo and colleagues in 2008. [16] They described a transperitoneal approach that involved mobilizing the bladder to get to the space of Retzius, followed by a horizontal cystotomy on the anterior surface of the bladder to get to the prostate adenoma. Several series have gone on to replicate this technique with slight modifications. [17, 18] Other series have described a transperitoneal, transvesical approach that does not require mobilizing the bladder [10, 11•]. The transvesical approach involves making a posterior cystotomy and using stay sutures on the hemibladder for retraction. The extraperitoneal approach is an alternative method for performing RASP and adopted from the approach to laparoscopic radical prostatectomy. [19, 20] Although no comparative series between various approaches have been reported, benefits of the extraperitoneal approach include avoiding intra-abdominal adhesions and compartmentalizing any potential hematoma or urinoma.

Comparative Outcomes

Previous literature has combined laparoscopic and robotic approaches into minimally invasive simple prostatectomy (MISP) to compare to OSP. The largest comparative study by Lucca et al. [21] was a meta-analysis which looked at 27 studies that included 764 patients. After an extensive analysis, the authors concluded that MISP, while taking longer, offered similar improvements in maximum flow rate (Qmax) and International Prostate Symptom Score (IPSS) as the open approach. However, MISP was noted to have less blood loss and shorter hospital stay. Parsons et al. [6] looked at the nationwide inpatient sample (NIS) from 1998 to 2010 and compared 6027 patients that underwent OSP to 193 MISP cases. While some non-significant trends were noted, the overall results showed MISP showed no difference compared to OSP.

Only two studies in the literature provide a direct comparison of RASP versus OSP. Hoy et al. [22] were the first to retrospectively describe four cases of RASP compared to 28 OSP cases from 2011 to 2013 in a Canadian academic center. While limited by a small sample size, the authors found that RASP was associated with a shorter hospital stay (2.3 vs. 5.5 days, p < 0.001), lower EBL (218.8 vs. 835.7 mL, p < 0.001), but a higher operative time (161 vs. 79 mins, p < 0.008) compared to OSP. The authors concluded that RASP deserved further investigation and consideration at Canadian centers performing robotic prostatectomies. Sorokin et al. [11•] retrospectively reviewed 167 simple prostatectomy cases over a 5-year period at a single institution. After 1:1 propensity score matching to reduce selection bias, 59 RASP cases were compared to 59 OSP cases. Similar to the comparative study described earlier, these authors found shorter hospital stay (1.5 vs. 2.6 days, p < 0.001), lower EBL (339 vs. 587 mL, p < 0.001), but longer operative times (161 vs. 93 mins, p < 0.001) compared to OSP, respectively. Functional outcomes were no different between the two techniques and the authors concluded that RASP offers several advantages over the open approach.

Despite the paucity of studies directly comparing the open and robotic approach, there is an abundance of individual series on RASP and OSP, respectively. Selected contemporary series [23–30] with respect to peri- and post-operative outcomes are described (Tables 1 and 2). We further explore the various parameters to compare both approaches.

Table 1 Perioperative and postoperative patient outcomes among RASP vs. OSP series
Full size table
Table 2 Functional, PSA, and complications among the selected RASP vs. OSP series
Full size table

Operative Times

One of the most criticized aspects of the robotic approach is the operative time. One RASP series reported a mean operative time of 274 min in 32 cases [13]. Compared to the longest OSP series which reported a mean operative time of 126 min [31], this is a significant downside to the robotic approach. While the overall data demonstrate OSP has shorter operative times on the order of 30 min to an hour, the increasing use of robotic surgery in urology may continue to decrease the disparity in operative times between RASP and the previously established standard of OSP.

Blood Loss and Transfusions

An important critique of OSP, as previously mentioned, is the elevated blood loss for patients who undergo this procedure. When looking at large national datasets [NIS], transfusion rates after OSP were found to be 20.9% compared with 10.8% for MISP. [6] That is, one in five patients that underwent OSP received a transfusion. However, this 50% reduction for the minimally invasive approach did not reach statistical significance. Our review also found a disparity in transfusion rates demonstrating that patients undergoing OSP were more than three to four times as likely to receive a blood transfusion as patients who underwent RASP. It is also important to note that transfusion rates can vary among institutions, surgeons, and patients based on local guidelines, personal preference, and comorbidities. [22] Without predetermined criteria for transfusion controlled in all patients in a given sample, transfusion rates are variable. Regardless, the general trend that OSP results in more perioperative blood loss is widely accepted and consistent with our review of the literature, which suggests that RASP is likely superior with respect to blood loss.

Hospital Length of Stay and Length of Catheterization

One of the main advantages of a minimally invasive approach is a decreased LOS. The NIS database comparing OSP and MISP noted a median 2 days shorter LOS for MISP, but this difference was not statistically significant. [6] Our review of the literature demonstrates that the average LOS in the hospital after RASP was at least half that of patients who underwent OSP. While LOS is certainly influenced by nonmedical factors such as local practice patterns and patients’ social situations, operative technique likely plays a major role. Although LOS was shorter, length of catheterization (LOC) was similar in both RASP and OSP. However, as Sorokin et al. [11•] suggest, RASP may, in fact, have shorter LOC but patients’ hospital stays are too short to remove the catheter at discharge, and thus, these patients have their catheters removed at their outpatient follow-up visit, increasing the LOC artificially. In contrast, patients undergoing OSP are typically in the hospital long enough to have their catheters removed before discharge. Again, while LOC is dependent to local practice patterns, it seems to be unaffected by the type of procedure patients are undergoing based on our review.

Adenoma Removal

All series included used a pre-operative criteria of transrectal ultrasound-based (TRUS) prostate volume > 80 mL for both OSP and RASP cohorts and therefore are appropriately comparable. Likewise, pre-operative PSA values ranged from 5 to 7 ng/mL in both approaches. Post-operative specimen weights were about equal in both approaches, ranging from 75 to 110 g in RASP series and 70–117 g in OSP series. Specimen weight of course depends on the timing of weighing the specimen and may differ if weighed immediately after specimen removal or by pathology report. Post-operative prostate-specific antigen (PSA) may be used as a surrogate of adenoma removal, and by this criteria, RASP and OSP are equally comparable with similar ranges of PSA decline seen in both approaches. As most of the RASP series were published in the last few years, it is premature to compare retreatment rates, although this will be an interesting variable in long-term studies.

Functional Outcomes

Functional outcomes are comparable between both approaches. Maximum flow rate (Qmax) showed a median 14 mL/s for RASP vs. a mean improvement of 15 mL/s for OSP post-operatively. Very rare reports of incontinence post-operatively are also noted in both approaches. IPSS also showed similar improvements among both robotic and open approaches with average reporting of mild symptoms after surgery compared to severe pre-operatively. These findings are consistent with the previous literature comparing the two approaches.

Complications

The morbidity associated with OSP was a major catalyst that spurred the search for alternative procedures to treat large gland BPH, such as RASP. In our review, major complications (Clavien ≥ 3) were almost double in OSP (10.6%) compared to RASP (5.6%). Series that report detailed complications often report severe bleeding, clots requiring intervention, and bladder neck/urethral stricture as the most common types of complications after simple prostatectomy.

Parons et al. [6] performed a unique comparison of morbidity among OSP and MISP by looking at patient safety indicators (PSIs) as established by the Agency for Healthcare Research and Quality (AHRQ). These quality measures assess complications of anesthesia, postoperative respiratory failure, and pulmonary embolus, among others. Their review showed that both approaches were safe as they showed relatively a low incidence of preventable adverse safety events. Despite the low frequency, room for improvement still remains in simple prostatectomy especially in improving processes for post-operative care.

Cost

Cost is another controversial topic when discussing robotic approaches to established urologic procedures such as OSP. Sutherland et al. [32] noted that RASP added an additional $2797 to the operating charges compared to OSP. However, Matei et al. [33] have shown RASP can be cheaper overall when factoring in the cost of hospitalization, transfusion rates, and need for continuous bladder irrigation (CBI). The additional social impact (i.e., savings from convalescence and back-to-work time) of robotics may be superior as well but cannot be quantified. Furthermore, Pariser et al. [7] noted significantly higher mean inflation-adjusted hospital charges if patients experienced a complication ($51,295) vs. those who did not ($32,305) after simple prostatectomy using the NIS database.

Robotic surgical instruments represent an essentially fixed cost that contributes to a significant portion of operative costs. [34] Innovative instrument use can be utilized in robotic surgery to drive down costs such as using one instrument for dual purposes (i.e., a mega needle driver can be used as both a needle driver and a retractor in RASP). Since most instruments have 10 lives and cost $2500, a savings of $250 per case can be estimated if a dedicated grasper/retractor is not additionally used. Future studies directly comparing costs are warranted.

Learning Curve

The learning curve for OSP has not been previously compared to RASP. Recently, a prospective, randomized series from Brazil comparing 65 consecutive patients undergoing suprapubic or retropubic prostatectomy during a resident’s learning curve was described. [31] The two techniques were all performed by first- or second-year residents but supervised by senior surgeons and compared in terms of surgical morbidity and functional outcomes. The mean EBL for the series was 1044 mL, higher than most OSP series and explained by the fact that residents performed the procedures at the beginning of their learning curve. There was also a high major complication rate with 26% being Clavien 3–4. Furthermore, 15.4% of patients required some re-endoscopic surgical intervention, 50% for clot evacuation. Functional outcomes, which included IPSS (5.56) and Qmax (19.8 mL/s), are comparable to other OSP series. Although a specific number for learning curve was not described, OSP is associated with higher morbidity in one’s early experience.

RASP has been growing in popularity as it is considered easier to adopt because of the familiarity with robotic surgery, especially radical prostatectomy. [35] An abstract presented at the 2017 World Congress of Endourology in Vancouver, BC, attempted to describe the learning curve for RASP among two surgeons. [36] Variables of interest, which included EBL, operative times, PSA reduction, and percentage tissue yield were plotted along their respective, consecutive cases and a logarithmic best-fit line was used to analyze the learning curve. All factors considered together, a learning curve of 5–10 cases was observed graphically. This is of course data from two highly experienced robotic surgeons commonly performing radical prostatectomies. The learning curve for novice robotic surgeons would be intriguing and desirable for future studies.

Conclusion

For men with large prostates, RASP is a valuable alternative to OSP. Men undergoing RASP have similar functional outcomes such as flow rates and symptom score improvement when compared to OSP. Despite longer operative times, patients undergoing RASP are shown to have a shorter hospital stay and lower morbidity profile. This is evidenced by both direct comparative studies and a number of individual RASP series that have been published after the older AUA guidelines in 2011. Therefore, RASP is a safe and effective alternative to OSP and appropriately no longer deemed “investigational” by the latest AUA guidelines on BPH. While further studies are needed on cost analysis and learning curve, it is evident that RASP will be increasingly implemented over OSP in centers with established robotic programs. Still, surgical management of large prostates should be individualized based on surgeon’s expertise, patient’s comorbidities, and availability of the technology.