How to Skin a Prostate: The Evolution of Robotic Prostatectomy

Abstract

Since the introduction of radical prostatectomy by Hugh Hampton Young in 1905, this surgery has undergone constant evolution. With increasing appreciation for the impact of functional preservation on cancer survivorship, urologists have been steadfast in their pursuit of precision surgery to eradicate cancer while maximally preserving the surrounding anatomical structures. In the 1990s and 2000s, the introduction of laparoscopic and robotic prostatectomy brought about welcome improvements including decreased intra-operative blood loss, decreased postoperative pain, shorter hospital length of stay, and faster recovery. Recognizing that focality of prostate cancer lends itself well to precision surgery, robotic surgeons have attempted to exploit the enhanced vision and dexterity provided by the instrument to further improve outcomes. Over the last decade, new techniques have been introduced to help reduce the incidence of incontinence and erectile dysfunction, the 2 most often encountered complications following prostatectomy.

Main

Since the introduction of radical prostatectomy by Hugh Hampton Young in 1905, this surgery has undergone constant evolution. With increasing appreciation for the impact of functional preservation on cancer survivorship, urologists have been steadfast in their pursuit of precision surgery to eradicate cancer while maximally preserving the surrounding anatomical structures. In the 1990s and 2000s, the introduction of laparoscopic and robotic prostatectomy brought about welcome improvements including decreased intra-operative blood loss, decreased postoperative pain, shorter hospital length of stay, and faster recovery. Recognizing that focality of prostate cancer lends itself well to precision surgery, robotic surgeons have attempted to exploit the enhanced vision and dexterity provided by the instrument to further improve outcomes. Over the last decade, new techniques have been introduced to help reduce the incidence of incontinence and erectile dysfunction, the 2 most often encountered complications following prostatectomy.

Anatomical Considerations

Previous anatomical studies have demonstrated that the dorsal venous complex (DVC) exits the penis between the dorsal aspect of the corpora cavernosa and emerges from the urogenital diaphragm to divide into the superficial, left and right lateral venous plexuses. ¹ Up to 37% of the cross-sectional urethral sphincter surface area overlap with the DVC at the prostatic apex. ² As part of the traditional anterior prostatectomy, a substantial portion of the sphincteric tissue may be severed during ligation of the DVC. Taking this into consideration, several of the continence preserving surgical techniques aim to preserve the DVC, along with its closely associated sphincteric structures.

Despite extensive research, the exact anatomy of the prostatic fasciae and their association with parasympathetic nerve fibers remain controversial. Substantial anatomical heterogeneity between patients makes it difficult to standardize a nerve sparing prostatectomy. In the past, the extent of nerves spared depended on the aggressiveness of the disease, with patients at low risk for extraprostatic extension (EPE) receiving closer dissection to the prostatic capsule whereas those at high risk undergoing wider dissection. In addition to the extracapsular nerves, the presence of nerves travelling within the pseudocapsule of the prostate has long been appreciated. ³ Recently, some groups have proposed precision prostatectomy, purposedly sparing prostate tissue along with intracapsular nerves to maximize erectile function recovery. ⁴

Retzius-sparing Prostatectomy

Retzius-sparing robotic prostatectomy was first introduced by Galfano and colleagues in 2010, ⁵ preserving all anatomical attachments anteriorly at and above the level of the DVC. This way, the interdigitating structures of the sphincteric mechanism with the DVC is spared, along with small accessory arterioles from the pudendal artery thought to provide additional vascular supply to the urethral sphincter, thus maximally preserving function. Up to 90% of men undergoing retzius-sparing prostatectomy reported recovery of continence using 0-1 safety pad within 7 days of catheter removal. ⁶ These favorable results came at no detriment to oncologic outcomes or recovery of sexual function. ⁷ Despite these results, there has been hesitancy in the adoption of this technique, mainly due to concerns regarding the unfamiliarity with this anatomical approach, the steep learning curve, and concern over increased risk of positive surgical margins.

Hood Technique

To alleviate the concerns regarding a completely unfamiliar approach, Wagaskar et al popularized the hood technique, through which a “hood” comprising of the detrusor apron, arcus tendinous, puboprostatic ligament, anterior vessels, and fibers of the detrusor muscle was preserved during prostate removal. ⁸ In essence, this technique parallels the results of the retzius-sparing prostatectomy by leaving sphincteric tissue untouched, resulting in quicker recovery of continence. In the initial report of the first 300 patients undergoing this procedure, continence rates were 21% at 1wk following catheter removal, and reaching 83% at 4wks. Mean console time was 118.5 mins, with a 6% positive surgical margin rate. Reassuringly, postoperative complications were comparable to that of traditional robotic assisted radical prostatectomy.

Precision Prostatectomy

The IDEAL study demonstrated feasibility, safety, and preliminary efficacy associated with precision prostatectomy in highly select men diagnosed with prostate cancer. ⁴ Precision prostatectomy was developed to bridge the gap for treating men with intermediate-risk prostate cancer unfit for active surveillance, while aiming to avoid side effects associated with whole-gland therapies. This approach requires selecting men with unilateral intermediate risk disease and performing a conventional nerve sparing prostatectomy on the side of the dominant lesion, while deliberately preserving a 5-10 mm rim of tissue including all layers of Denonvilliers’ fascia, erectogenic nerves, along with the seminal vesicle/ejaculatory duct complex within the prostatic capsule, to minimize treatment related side-effects. To avoid incomplete cancer resection, the remnant prostatic tissue is sampled intraoperatively via frozen section, with completion of surgical resection if cancer was present.

In the IDEAL study, patients diagnosed with intermediate risk prostate cancer, and dominant unilateral lesion with Gleason ≤ 4 + 3 disease with no contralateral Gleason ≥ 4 lesion were selected to undergo precision prostatectomy. Sood et al ⁴ reported 90.9% 0-pad rate at 12mo, along with 90.2% return of potency in preoperatively potent men, with a median time to sexual potency of 4mo (IQR 4-12). The procedure was also oncologically sound, with an estimated 93.4% recurrence free survival at 36mo.

Although the early results from these innovative studies demonstrated safety along with adequate cancer control, the indolent course of prostate cancer following surgical resection makes it too early to draw any definitive conclusions. While the improvement on post-surgical quality of life by these technical modifications is clear, the potential long-term compromise to cancer control requires careful consideration and further follow-up. On the other hand, how these surgeries compare against the less invasive focal ablative therapies in terms of long-term cancer control warrants further study. As more efficacious systemic/local therapies become available in the management of localized prostate cancer, the use of these novel surgical approaches will continue to evolve.

As the morbidities associated with these procedures are reduced, their implementation in the high-stakes salvage setting has also been investigated. Indeed, several groups have reported faster continence recovery following the retzius-sparing approach in patients suffering radiation failure for localized prostate cancer. ⁹ A deeper read into the data, however, reveals that these results were derived from highly-selected men, who were younger, and with predominantly organ-confined disease. In a higher risk cohort, positive margin rate was found to be unacceptably high, at 50% with retzius-sparing prostatectomy. ¹⁰ In our hands, performance of retzius-sparing or hood preservation prostatectomy did not obviate the dreaded problem of incontinence in post-radiation patients. For this reason, we continue to rely on focal, ablative therapies in such clinical scenarios.

The mantra “First do no harm” rings true with surgical innovation. Along with the excitement of introducing new approaches, surgical pioneers need to weigh the risks of compromising oncologic outcomes. While clear rationale supports the adoption of the retzius-sparing and hood preservation approaches, the justification for precision prostatectomy is less compelling. Sandwiched between whole gland therapy for high-risk disease vs ablative therapy and active surveillance for low-risk disease, the advantage of this procedure seems less defensible. Additionally, remnant prostatic tissue will continue to produce PSA, undercutting the ease of postoperative cancer surveillance, one of the major attractions for selecting radical prostatectomy for the treatment of localized prostate cancer. In all, 10/88 patients in the IDEAL study were found to have clinically detectable recurrent prostate cancer in the remnant prostatic tissue, six of whom elected to undergo repeated surgery to remove the remaining disease. Although these salvage procedures were shown to be feasible and safe in the hands of expert surgeons conducting the study, it nonetheless represents an additional trip to the operating theatre requiring repeated general anaesthesia. Even for those with residual Gleason 3 + 3 disease who chose to be placed on active surveillance, the mandated periodic biopsies will undoubtedly diminish post-surgical quality of life. With all of these considerations, precision prostatectomy seems to have a comparable benefit profile as salvage focal ablative therapy, but at a much higher cost due to the requirement of intraabdominal surgery.

Surgery has long been established as one of the pillars of cancer therapy. Long years of dedicated training and a relentless pursuit of perfection is required on the road to becoming a competent surgeon. However, with the advent of molecularly targeted therapy and immunotherapy, surgery’s foundational role in cancer care seems to be challenged. With more and more effective systemic treatment options, surgery is often relegated to the treatment of last resort. Under these circumstances, it is especially important for surgeons to be thoughtful about their approach, and to continue innovating responsibly, taking into consideration the limitations of surgery while being keenly aware of its side-effects. Only this way we can continue to impact cancer outcomes in a meaningful way.