Robot-Assisted Versus Open Simple Prostatectomy for Benign Prostatic Hyperplasia in Large Glands: A Propensity Score–Matched Comparison of Perioperative and Short-Term Outcomes

Introduction

Open simple prostatectomy (OSP) is considered a standard treatment for large prostate glands (≥80 g) associated with lower urinary tract symptoms (LUTS) by both the American Urological Association (AUA) and European Association of Urology (EAU) ^1,2 Although the functional outcomes of OSP are favorable (symptom score, flow, and postvoid residual [PVR]), OSP may be associated with significant estimated blood loss (EBL), relatively high rates of transfusions, and longer hospital length of stay (LOS). ^3,4 For this reason, minimally invasive treatments for large, obstructing glands are increasingly pursued, and notably, OSP cases have been decreasing as reflected by national trends. ^{5 –8}

Since the first description of robot-assisted simple prostatectomy (RASP) by Sotelo and colleagues ⁹ in 2008, the reported experience with RASP has also been increasing worldwide. ^4,10 This is likely in part due to the increased comfort of urologists with robotic surgery. In addition, many urologic surgeons are now familiar with the robot-assisted laparoscopic radical prostatectomy, which may allow a smooth transition to RASP. ¹¹ Furthermore, RASP may be easier to adopt than the more challenging laparoscopic simple prostatectomy (LSP) ¹² or holmium laser enucleation of prostate (HoLEP). ^13,14

The current AUA and EAU guidelines support OSP for large-volume glands, but describe RASP as investigational due to the lack of sufficient studies demonstrating value. ^1,2 Our primary objective was to compare the perioperative outcomes between the two approaches and secondarily, to compare functional outcomes. Propensity matching was employed to ensure groups were statistically similar in relevant variables in the preoperative setting and to help eliminate selection bias. Herein, we present our initial RASP experience compared with OSP using a propensity matched analysis in an effort to contribute to the growing body of literature demonstrating RASP as a safe and effective treatment for large-volume benign prostatic hyperplasia (BPH).

Materials and Methods

The Institutional Review Board approval was obtained to retrospectively review patients who underwent simple prostatectomy from July 2012 to December 2016. Indications for surgery included prostate volume ≥80 cm³ and LUTS refractory to medical treatment. Patients were separated into two groups: those who underwent OSP (n = 103) and those who underwent RASP (n = 64). Demographics, clinical, and pathological data were collected. Operative time was obtained from the anesthesia records. For OSP, operative time was measured from time to dressing placement. For robotic cases, operative time was measured from placement of the Veress needle to dressing placement. Percentage of hematocrit (HCT) drop was calculated from the preoperative HCT to the lowest HCT during admission. Percentage of prostate volume reduction was calculated based on the pathological specimen weight divided by the transrectal ultrasound (TRUS) prostate volume. Postoperative International Prostate Symptom Score (IPSS), PVR, and maximal flow rate (Qmax), were obtained between 1 and 3 months follow-up. Complications were graded based on the Clavien–Dindo classification.

The OSP technique was performed through a modified retropubic approach with blunt adenoma enucleation and bladder neck reconstruction without use of a suprapubic tube. RASP procedures were performed using the da Vinci Si surgical system (Intuitive Surgical, Sunnyvale, CA) using a transperitoneal approach similar to that described by Sotelo and colleagues ⁹ with several slight variations. Continuous bladder irrigation was started immediately after bladder closure and turned off in the morning of postoperative day 1.

Statistical analysis was performed using IBM^® SPSS^®, version 22. Due to potential bias in patient selection, propensity score matching was performed to ensure the groups were similar in terms of relevant preoperative variables. Propensity scores were calculated by logistic regression model using five covariates, including age, body mass index, race, Charlson comorbidity index, and TRUS prostate volume. Nearest-neighbor 1:1 matching ¹⁵ was performed to match similar neighbor propensity scores using the SPSS propensity score–matching package. Patients with missing data in any of the matched variables were excluded from the propensity score–matched comparison. Propensity score matching resulted in our ability to compare 59 RASP to 59 OSP cases. Continuous variables were compared using either student's t-test or Mann–Whitney U test. Categorical variables were analyzed using either Pearson's chi-square or Fisher's exact test. Two-tailed hypothesis tests were used in each case, and a p-value of ≤0.05 was considered statistically significant.

Results

Preoperative patient demographics and clinical data before and after propensity score matching are shown in Table 1. After propensity score matching, RASP (n = 59) vs OSP (n = 59) showed similar mean age (68.7 vs 68.1 years, p = 0.657), prostate volume (136.9 vs 144.3 cm³, p = 0.396), number of catheter-dependent patients (29% vs 31%, p = 0.84), and mean IPSS (18.8 vs 17.9, p = 0.926).

Peri- and postoperative patient outcomes before and after propensity score matching are displayed in Table 2. After propensity score matching, RASP vs OSP, showed a statistically significant shorter LOS (1.5 vs 2.6 days, p < 0.001), but longer mean operative times (161.4 vs 93.0 minutes, p < 0.001). Statistically significant differences were also noted between RASP vs OSP with lower EBL (338.9 vs 587.3 mL, p < 0.001), and lower percentage HCT drop (12.3% vs 19.5%, p = 0.001) favoring the robotic approach. Transfusion rates also occurred half as often in the RASP group compared with the OSP group, but this was not statistically significant (3.4% vs 6.8%, p = 0.679). Specimen weight was not statistically significant after propensity score matching (82.9 vs 91.8, p = 0.217) nor was percentage of prostate volume reduction (61.4% vs 65.2%, p = 0.405). The RASP group had lower PVR compared with OSP after propensity score matching (3.5 vs 48 mL, p = 0.007). In the entire cohort, prostatic adenocarcinoma (CaP) was incidentally detected in 8 RASP and 13 OSP cases on final pathology. All RASP cases of CaP were identified as low-volume Gleason score 3 + 3 (grade group 1). Low-volume Gleason score 3 + 4 (grade group 2) CaP was found in 4/13 of the OSP cases. One case of Gleason 4 + 5 (grade group 5), 5% CaP was found incidentally in an 85 year old after OSP. Conservative management was elected with annual monitoring of his prostate-specific antigen (PSA).

PSA and functional outcomes after propensity score matching are shown in Table 3. Both RASP and OSP had similar percentage decrease in PSA (87.7% vs 90.7%, p = 0.44, respectively). The decrease in IPSS (11.5 vs 10.8, p = 0.884) and improvements in Qmax (12.6 vs 11.5, p = 0.36) were comparable between RASP and OSP, respectively. All 17 patients who were catheter dependent preoperatively were catheter free after RASP and 17 of 18 (94.4%) were catheter free after OSP, but not statistically different (p = 0.496). All patients were specifically asked about urinary stress incontinence at the first postoperative visit after catheter removal; none in either cohort complained of urinary incontinence.

Complication rates between RASP vs OSP are shown in Table 4. After propensity score matching, lower rates of all complications were seen in RASP (19%) vs OSP (27%), but this difference was not statistically significant (p = 0.381). The most common major complications (Clavien–Dindo 3–5) after OSP included bladder neck contracture in two patients and clot retention requiring intervention in two patients. Two Clavien–Dindo grade 3 complications occurred after RASP. These included meatal stenosis requiring dilation and clot retention requiring clot evacuation in the operating room. Mean follow-up was 6 months for RASP cohort and 13 months for the OSP cohort.

Discussion

The current AUA and EAU guidelines indicate that there is insufficient published data to recommend a robotic approach for the treatment of symptomatic BPH in larger prostate glands. ^1,2 However, there have been a multitude of studies describing RASP as a safe and effective procedure. ^4,10,16 Only one study previous to ours directly compared RASP to OSP, but only four RASP cases were reported in that series. ³ Our cohort represents the largest single-center experience comparing RASP to OSP and the only propensity matched series. In this study, we confirm RASP is associated with a shorter hospital stay, lower perioperative blood loss, but with longer operative time.

When looking at large national datasets (nationwide inpatient sample [NIS]), transfusion rates after OSP were found to be 20.9% compared with 10.8% for minimally invasive simple prostatectomy. ⁶ Interestingly, this ∼50% reduction seen with robotic prostatectomy is nearly identical to what we found, although our series had a significantly less number of absolute transfusions in each group. Seeming to confirm our experience, a recent review of 13 RASP series showed transfusion rates for RASP are likely even lower than reported by NIS, averaging 2.1% ³ and is more consistent with the rate seen in our series (3.4%). However, the difference in transfusion rates were not statistically different in our series, which may be due to the small number of events in each group in addition to the uncharacteristically low number of transfusion in the OSP group. Also of note, the transfusions that occurred happened early in the RASP series (first and ninth case). No transfusions have been reported since (subsequent 50 cases). Lastly, in this study, we report the initial RASP experience (from first patient onward) compared with what could be considered a very mature OSP experience.

The longer operative time with the robotic approach has been reported in other published series as well. ^9,10,17 However, this is not seen in every series and may not be the case as more RASP procedures are performed. In our series, flexible cystoscopy was performed early in the experience during apical dissection to better define the boundaries of the adenoma and avoid sphincteric injury. With experience, this step was no longer performed, thus decreasing operative time. A more contemporary series comparing RASP (n = 81) to HoLEP (n = 45) showed a median operative time of 105 minutes for RASP, which is comparable to most OSP series. ¹⁸ In addition, flexible cystoscopy was performed early in our series during apical dissection to better define the boundaries of the adenoma and avoid injury to the external sphincter. With experience, this step is no longer performed which has decreased the operative times. No patients were incontinent 1 month after surgery further demonstrating that this step becomes unnecessary with experience.

Longer catheterization times were also found in our RASP cohort, but this is not a consistent finding throughout the literature. This may be a result of RASP patients leaving the hospital early (first postoperative day) with an outpatient follow-up appointment for catheter removal. Conversely, patients after OSP usually had their catheter removed on their final hospital day (day 3), which is in part due to their longer hospital stays.

Our robotic technique has undergone several modifications that we believe are advantageous. First, the bladder is not mobilized and the retropubic space is not developed, thus reducing operative time and minimizing the disruption of the natural tissue planes. Second, we feel the placement of a hemostatic product in the prostatic fossa with compression by the Foley balloon helps to further improve hemostasis and shorten hospital stay. In addition, the robotic approach offers precise cautery and suturing compared with the open approach, minimizing blood loss. The trigone can also be precisely recreated to avoid future bladder neck contractures (4% in OSP group). A barbed suture may also be used to recreate the trigone and close the bladder, further improving operative efficiency.

The comparison of RASP to OSP remains relevant as OSP remains the standard for which large-volume gland treatment is measured and given that the majority of simple prostatectomies are still performed through the open approach. ^5,6 However, recent trends in treatment of large-volume BPH has shown other minimally invasive modalities, such as photoselective vaporization of prostate (PVP), and bipolar transurethral resection of prostate (TURP), to be effective. However, it is not clear that these modalities are equivalent when comparing tissue removed and retreatment rates. If using PSA as a surrogate for adenoma removal, using the GreenLight™ 180W XPS™ would be considered inferior. Studies have shown PSA reductions ranging from 30% to 46% with GreenLight PVP, ^19,20 whereas our RASP series demonstrates an 87.7% reduction. Furthermore, retreatment for patients for large glands tends to be high using many of the transurethral techniques. For example, retreatment after PVP is more frequent in patients with larger glands (∼120 g) ¹⁹ and TURP retreatment rates for larger glands range from 5% to 10%. ^21,22 No patient in our RASP series with an average volume of 137 g has required retreatment, although the follow-up is somewhat limited.

HoLEP has shown comparable functional outcomes to OSP, but with reduced LOS, EBL, and transfusion rates. ^23,24 Recently, Umari and colleagues ¹⁸ retrospectively reviewed the first comparative series between RASP (n = 81) and HoLEP (n = 45). Both groups showed similar median operative times, postoperative hemoglobin, functional outcomes, and complication rates. HoLEP patients benefitted from a shorter LOS (2 vs 4 days), and a larger amount of prostate tissue resected (112 vs 89 g). However, HoLEP patients suffered from a higher rate of transient urinary incontinence (8.9% vs 1.2%). In our series of RASP patients, the average LOS for RASP was 1.5 days, rivaling the reported LOS for HoLEP and none of our patients experienced transient or permanent urinary incontinence. While there is little question that HoLEP offers a more minimally invasive approach than RASP, there remains the question of surgeon adaptability. It has also been estimated that 40–60 cases are necessary to become proficient in HoLEP. ¹⁴ While assessing the learning curve for RASP is outside the scope of this article, the RASP procedure may offer a natural transition for surgeons who have experience in robotic surgery. ^11,25

An additional criticism of the RASP procedure is high cost. Cost comparison of RASP to LSP was reported by Sotelo and colleagues ⁹ in a report of seven RASP procedures. With a mean operative time of 195 minutes for RASP, the average cost of the robotic approach was $12,093.02 compared with $10,465.11 for LSP. The authors concluded the difference was marginal compared with the multiple benefits of RASP. Matei and colleagues ²⁶ also compared cost between RASP and OSP (35 RASP cases compared with 63 OSP cases). They found that RASP was economically advantageous largely due to higher costs associated with the longer duration of hospitalization for OSP. Furthermore, the authors pointed out that the additional social impact (i.e., savings from convalescence and back-to-work time) of robotics would likely have been superior but could not be quantified. While higher equipment costs are unavoidable, our current surgical approach has been modified to use only three robotic instruments, minimizing this affect. A careful cost analysis in a modern series is needed to fully explore the question of cost.

Several limitations of our study exist. The retrospective nature of our study is a limitation. However, propensity score matching was implemented to reduce selection bias as there was a slight tendency toward larger glands for OSP. An additional limitation to our study is follow-up. Because RASP is a relatively novel procedure at our institution, longer-term outcomes cannot be assessed currently. That being said, no retreatments for suboptimal tissue removal were needed to this date for both RASP and OSP at a mean 6 and 13 months follow-up, respectively. Lastly, the OSP cohort represented a mature cohort of patients (patients selected well into the learning curve of the surgeons), whereas the RASP patient cohort was selected beginning with the first RASP performed. This bias cannot be controlled for by propensity match, but if anything would strengthen the conclusions drawn regarding blood loss and hospital stay favoring RASP.

Conclusion

Robotic simple prostatectomy is a safe and effective approach for the treatment of symptomatic patients with very large prostate glands. RASP offers several advantages to OSP, including decreased blood loss and decreased length of hospital stay but with longer operative time. Further studies are needed examining cost and comparing robotic simple prostatectomy to other contemporary treatment modalities in the treatment of large glands.