Bilateral Cavernous Nerve Interposition Grafting During Radical Retropubic Prostatectomy: Memorial Sloan-Kettering Cancer Center Experience

An update on the current status and future prospects of erectile dysfunction following radical prostatectomy

BACKGROUND

Radical prostatectomy (RP) and radiation treatment are standard options for localized prostate cancer. Even though nerve-sparing techniques have been increasingly utilized in RP, erectile dysfunction (ED) due to neuropraxia remains a frequent complication. Erectile function recovery rates after RP remain unsatisfactory, and many men still suffer despite the availability of various therapies.

OBJECTIVE

This systematic review aims to summarize the current treatments for post-RP-ED, assess the underlying pathological mechanisms, and emphasize promising therapeutic strategies based on the evidence from basic research.

METHOD

Evaluation and review of articles on the relevant topic published between 2010 and 2021, which are indexed and listed in the PubMed database.

RESULTS

Phosphodiesterase type 5 inhibitors, intracavernosal and intraurethral injections, vacuum erection devices, pelvic muscle training, and surgical procedures are utilized for penile rehabilitation. Clinical trials evaluating the efficacy of erectogenic drugs in this setting are conflicting and far from being conclusive. The use of androgen deprivation therapy in certain scenarios after RP further exacerbates the already problematic situation and emphasizes the need for effective treatment strategies.

CONCLUSION

This article is a detailed overview focusing on the pathophysiology and mechanism of the nerve injury developed during RP and a compilation of various strategies to induce cavernous nerve regeneration to improve erectile function (EF). These strategies include stem cell therapy, gene therapy, growth factors, low-intensity extracorporeal shockwave therapy, immunophilins, and various pharmacological approaches that have induced improvements in EF in experimental models of cavernous nerve injury. Many of the mentioned strategies can improve EF following RP if transformed into clinically applicable safe, and effective techniques with reproducible outcomes.

Regenerative technology to restore and preserve erectile function in men following prostate cancer treatment: evidence for penile rehabilitation in the context of prostate cancer survivorship

Introduction

Erectile dysfunction (ED) following prostate cancer treatment is not uncommon and penile rehabilitation is considered the standard of care in prostate cancer survivorship (PCS), where both patient and his partner desire to maintain and/or recover pre-treatment erectile function (EF). There is a clinical interest in the role of regenerative therapy to restore EF, since existing ED treatments do not always achieve adequate results.

Aim

To review regenerative therapies for the treatment of ED in the context of PCS.

Materials and Methods

A review of the existing PubMed literature on low-intensity extracorporeal shockwave therapy (LIESWT), stem cell therapy (SCT), platelet-rich plasma (PRP), gene therapy, and nerve graft/neurorrhaphy in the treatment of ED and penile rehabilitation, was undertaken.

Results

IESWT promotes neovascularization and neuroprotection in men with ED. While several systematic reviews and meta-analyses showed positive benefits, there is limited published clinical data in men following radical prostatectomy. Cellular-based technology such as SCT and PRP promotes cellular proliferation and the secretion of various growth factors to repair damaged tissues, especially in preclinical studies. However, longer-term clinical outcomes and concerns regarding bioethical and regulatory frameworks need to be addressed. Data on gene therapy in post-prostatectomy ED men are lacking; further clinical studies are required to investigate the optimal use of growth factors and the safest vector delivery system. Conceptually interpositional cavernous nerve grafting and penile re-innervation technique using a somatic-to-autonomic neurorrhaphy are attractive, but issues relating to surgical technique and potential for neural 'regeneration' are questionable.

Conclusion

In contrast to the existing treatment regime, regenerative ED technology aspires to promote endothelial revascularization and neuro-regeneration. Nevertheless, there remain considerable issues related to these regenerative technologies and techniques, with limited data on longer-term efficacy and safety records. Further research is necessary to define the role of these alternative therapies in the treatment of ED in the context of penile rehabilitation and PCS.

Surgical Techniques for Managing Post-prostatectomy Erectile Dysfunction

Purpose of Review

Due to the increasing numbers of radical prostatectomies (RP) performed for prostate cancer, a substantial number of patients are now suffering from post-operative erectile dysfunction (ED). The aim of this study is to summarize the current literature on surgical techniques for managing post-prostatectomy erectile dysfunction.

Recent Findings

The PubMed database was searched for English-language articles published up to Jan 2017 using the following search terms: “prostatectomy AND erectile dysfunction”, “prostatectomy AND penile prostheses”, and “prostatectomy AND penile implants”. All of the studies that evaluated medical treatment were excluded. In the last few decades, the understanding of the anatomy of the male pelvis and prostate has improved. This has led to significant changes in the nerve-sparing radical prostatectomy techniques, with the aim of preserving post-surgical erectile function (EF). In this scenario, the prostate vascular supply and the anatomy of the neurovascular bundles have a central role. Penile prosthesis implantation is considered the third-line treatment option for RP ED patients, and they have been reported to be a very successful treatment with the highest patient satisfaction rate.

Summary

Considering the failure of penile rehabilitation, and the lack of evidence for accessory pudendal artery (APA) preservation and nerve graft, nerve-sparing surgery and penile prostheses represent, today, the only methods to permanently and definitively preserve or erectile function after RP.

Current rehabilitation strategy: clinical evidence for erection recovery after radical prostatectomy

Erectile function (EF) recovery remains a prominent functional outcome underachievement of radical prostatectomy (RP), despite the success of anatomic “nerve-sparing” technique and its recent refinements in the modern surgical era. Delayed (for as much as a few years) or incomplete (partial and unusable) EF recovery commonly occurs in many men still today undergoing this surgery. “Penile rehabilitation”, alternatively termed “EF rehabilitation”, originated formally as a therapeutic practice approximately 15 years ago for addressing post-RP erectile dysfunction (ED) beyond conventional ED management. Although the premise of this therapy is conceptually sound and generally accepted, in reference to the implementation of strategies for promoting EF recovery to a naturally functional level in the absence of erectile aids (distinct from the premise of conventional ED management), the optimal manner and efficacy of currently suggested therapeutic strategies are far less established. Such strategies include regimens of standard ED-specific therapies (e.g., oral, intracavernosal, and intraurethral pharmacotherapies; vacuum erection device therapy) and courses of innovative interventions (e.g., statins, erythropoietin, angiotensin receptor blockers). An endeavor in evolution, erection rehabilitation may ideally comprise an integrative program of sexual health management incorporating counseling, coaching, guidance toward general health optimization and application of demonstrably effective “rehabilitative” interventions. Ongoing intensive discovery and rigorous investigation are required to establish efficacy of therapeutic prospects that fulfill the intent of post-RP erection rehabilitation.

Interpositional Nerve Grafting of the Prostatic Plexus after Radical Prostatectomy

Background:

Injury to the prostatic plexus may occur during radical prostatectomy even with the use of minimally invasive techniques. Reconstruction of these nerves by interpositional nerve grafting can be performed to reduce morbidity. Although the feasibility of nerve reconstruction has been shown, long-term functional outcomes are mixed, and the role of nerve grafting in these patients remains unclear.

Methods:

A retrospective study was performed on 38 consecutive patients who underwent immediate unilateral or bilateral nerve reconstruction after open prostatectomy. Additionally, 53 control patients who underwent unilateral, bilateral, or non–nerve-sparing open prostatectomy without nerve grafting were reviewed. Outcomes included rates of urinary continence, erections sufficient for sexual intercourse, and ability to have spontaneous erections. Analysis was performed by stratifying patients by D’Amico score and laterality of nerve involvement.

Results:

Unilateral nerve grafting conferred no significant benefit compared with unilateral nerve-sparing prostatectomy. Bilateral nerve-sparing patients demonstrated superior functional outcomes compared with bilateral non–nerve-sparing patients, whereas bilateral nerve-grafting patients displayed a trend toward functional improvement. With increasing D’Amico score, there was a trend toward worsening urinary continence and erectile function regardless of nerve-grafting status.

Conclusions:

In the era of robotic prostatectomy, interpositional nerve reconstruction is not a routine practice. However, the substantial morbidity experienced in patients with bilateral nerve resections remains unacceptable, and therefore, nerve grafting may still improve functional outcomes in these patients. Further investigation is needed to improve the potential of bilateral nerve grafting after non–nerve-sparing prostatectomy.

Three-year outcomes of recovery of erectile function after open radical prostatectomy with sural nerve grafting

INTRODUCTION

Optimal oncologic control of higher stage prostate cancers often requires sacrificing the neurovascular bundles (NVB) with subsequent postoperative erectile dysfunction (ED), which can be treated with interposition graft using sural nerve.

AIMS

To examine the long term outcome of sural nerve grafting (SNG) during radical retropubic prostatectomy (RRP) performed by a single surgeon.

METHODS

Sixty-six patients with clinically localized prostate cancer and preoperative International Index of Erectile Function (IIEF) score >20 who underwent RRP were included. NVB excision was performed if the risk of side-specific extra-capsular extension (ECE) was >25% on Ohori' nomogram. SNG was harvested by a plastic surgeon, contemporaneously as the urologic surgeon was performing RRP. IIEF questionnaire was used pre- and postoperatively and at follow-up.

MAIN OUTCOME MEASURES

Postoperative IIEF score at three years of men undergoing RRP with SNG. Recovery of potency was defined as postoperative IIEF-EF domain score >22.

RESULTS

There were 43 (65%) unilateral SNG and 23 (35%) bilateral SNG. Mean surgical time was 164 minutes (71 to 221 minutes).The mean preoperative IIEF score was 23.4+1.6. With a mean follow-up of 35 months, 19 (28.8%) patients had IIEF score >22. The IIEF-EF scores for those who had unilateral SNG and bilateral SNG were 12.9+4.9 and 14.8+5.3 respectively. History of diabetes (P=0.001) and age (P=0.007) negatively correlated with recovery of EF. 60% patients used PDE5i and showed a significantly higher EF recovery (43% vs. 17%, P=0.009).

CONCLUSIONS

SNG can potentially improve EF recovery for potent men with higher stage prostate cancer undergoing RP. The contemporaneous, multidisciplinary approach provides a good quality graft and expedited the procedure without interrupting the work-flow.

Cancer control and functional outcomes after radical prostatectomy as markers of surgical quality: analysis of heterogeneity between surgeons at a single cancer center

BACKGROUND

Previous studies have shown that complications and biochemical recurrence rates after radical prostatectomy (RP) vary between different surgeons to a greater extent than might be expected by chance. Data on urinary and erectile outcomes, however, are lacking.

OBJECTIVE

In this study, we examined whether between-surgeon variation, known as heterogeneity, exists for urinary and erectile outcomes after RP.

DESIGN, SETTING, AND PARTICIPANTS

Our study consisted of 1910 RP patients who were treated by 1 of 11 surgeons between January 1999 and July 2007.

INTERVENTION

All patients underwent RP at Memorial Sloan-Kettering Cancer Center.

MEASUREMENTS

Patients were evaluated for functional outcome 1 yr after surgery. Multivariable random effects models were used to evaluate the heterogeneity in erectile or urinary outcome between surgeons, after adjustment for case mix (age, prostate-specific antigen, pathologic stage and grade, comorbidities) and year of surgery.

RESULTS AND LIMITATIONS

We found significant heterogeneity in functional outcomes after RP (p<0.001 for both urinary and erectile function). Four surgeons had adjusted rates of full continence <75%, whereas three had rates >85%. For erectile function, two surgeons in our series had adjusted rates <20%; another two had rates >45%. We found some evidence suggesting that surgeons' erectile and urinary outcomes were correlated. Contrary to the hypothesis that surgeons "trade off" functional outcomes and cancer control, better rates of functional preservation were associated with lower biochemical recurrence rates.

CONCLUSIONS

A patient's likelihood of recovering erectile and urinary function may differ depending on which of two surgeons performs his RP. Functional preservation does not appear to come at the expense of cancer control; rather, both are related to surgical quality.

Tissue engineering and stem cells: basic principles and applications in urology

To overcome problems of damaged urinary tract tissues and complications of current procedures, tissue engineering (TE) techniques and stem cell (SC) research have achieved great progress. Although diversity of techniques is used, urologists should know the basics. We carried out a literature review regarding the basic principles and applications of TE and SC technologies in the genitourinary tract. We carried out MEDLINE/PubMed searches for English articles until March 2010 using a combination of the following keywords: bladder, erectile dysfunction, kidney, prostate, Peyronie's disease, stem cells, stress urinary incontinence, testis, tissue engineering, ureter, urethra and urinary tract. Retrieved abstracts were checked, and full versions of relevant articles were obtained. Scientists have achieved great advances in basic science research. This is obvious by the tremendous increase in the number of publications. We divided this review in two topics; the first discusses basic science principles of TE and SC, whereas the second part delineates current clinical applications and advances in urological literature. TE and SC applications represent an alternative resource for treating complicated urological diseases. Despite the paucity of clinical trials, the promising results of animal models and continuous work represents the hope of treating various urological disorders with this technology.

Histologic and electrophysiological study of nerve regeneration using a polyglycolic acid-collagen nerve conduit filled with collagen sponge in canine model

OBJECTIVES

To determine the rate of achieving electrophysiologically proved functional recovery by autonomic nerve regeneration, with the aid of an artificial nerve conduit.

METHODS

A polyglycolic acid (PGA) collagen nerve conduit filled with collagen sponge was interposed in a 10-mm-long gap of the right hypogastric nerve (HGN) in 16 dogs. Histologic evaluation of nerve regeneration and electrophysiological analysis at 2 weeks and 2, 3, 4, 5, 6, 7, and 8 months (n = 2, each) after surgery was performed, measuring the responses for the spermatic ducts (SD), bladder neck (BN), and prostate contraction, by stimulating the right lumbar splanchnic nerves (LSNs) from L2 to L4, after transection of the left HGN to eliminate substitutive pathways.

RESULTS

Two months after implantation, the regenerated neurofilaments were successfully extended through the graft from the proximal-to-distal direction. In 2 control dogs, electrostimulation of the right LSNs induced elevation of the intraluminal pressure of the SD, elevation of the BN pressure, and prostate contraction. No responses were observed in all dogs up to 6 months of follow-up after implantation. In 1 dog with a 7-month follow-up, electrostimulation elicited elevation of BN pressure alone. In both dogs with an 8-month follow-up, electrostimulation induced similar responses to control in all SD, BN, and prostate; however, after excision of the area of the interposed right HGN, no response was observed.

CONCLUSIONS

These results proved that regeneration of a 10-mm gap of the HGN, using a novel PGA-collagen nerve conduit could be achieved within 8 months.

Prostate size is associated with surgical difficulty but not functional outcome at 1 year after radical prostatectomy

PURPOSE

We assessed the impact of prostate size on operative difficulty as measured by estimated blood loss, operating room time and positive surgical margins. In addition, we assessed the impact on biochemical recurrence and the functional outcomes of potency and continence at 1 year after radical prostatectomy as well as postoperative bladder neck contracture.

MATERIALS AND METHODS

From 1998 to 2007, 3,067 men underwent radical prostatectomy by 1 of 5 dedicated prostate surgeons with no neoadjuvant or adjuvant therapy. Pathological specimen weight was used as a measure of prostate size. Cox proportional hazards and logistic regression analysis was used to study the association between specimen weight, and biochemical recurrence and surgical margin status, respectively, controlling for adverse pathological features. Continence and potency were analyzed controlling for age, nerve sparing status and surgical approach.

RESULTS

With increasing prostate size there was increased estimated blood loss (p = 0.013) and operative time (p = 0.004), and a decrease in positive surgical margins (84 of 632 [14%] for 40 gm or less, 99 of 862 [12%] for 41 to 50 gm, 78 of 842 [10%] for 51 to 65 gm, 68 of 731 [10%] for more than 65 gm, p <0.001). Biochemical recurrence was observed in 186 of 2,882 patients followed postoperatively and was not significantly associated with specimen weight (p = 0.3). Complete continence was observed in 1,165 of 1,422 patients (82%) and potency in 425 of 827 (51%) at 1 year. Specimen weight was not significantly associated with potency (p = 0.8), continence (p = 0.08) or bladder neck contracture (p = 0.22).

CONCLUSIONS

Prostate size does not appear to affect biochemical recurrence or 1-year functional results. However, estimated blood loss and operative time increased with larger prostate size, and positive surgical margins are more often observed in smaller glands.

Interposition nerve grafting during radical prostatectomy: cumulative review and critical appraisal of literature

In 1997, the first report of sural nerve interposition grafting during radical prostatectomy was published in Urology. The favorable findings in this initial pilot study generated numerous follow-up reports that have demonstrated conflicting and contradictory outcomes. Certainly, controversy exists regarding the true benefit of nerve grafting. This review will objectively and critically summarize the salient literature, discuss evolving techniques, and offer insight into the future of interposition grafting in the current era of clinically localized prostate cancer and robotic prostatectomy.

Randomized phase II trial evaluation of erectile function after attempted unilateral cavernous nerve-sparing retropubic radical prostatectomy with versus without unilateral sural nerve grafting for clinically localized prostate cancer

BACKGROUND

Nonrandomized studies of unilateral nerve-sparing (UNS) radical prostatectomy (RP) have reported improved recovery of erectile function if the sacrificed cavernous nerve is reconstructed with a sural nerve graft (SNG).

OBJECTIVE

To determine whether UNS RP plus SNG results in a 50% relative increase in potency at 2 yr compared to UNS RP alone.

DESIGN, SETTING, AND PARTICIPANTS

The study enrolled patients from October 2001-May 2006 from a single academic center and was randomized, open label. Participants were men with localized prostate cancer recommended for UNS RP, less than 66 yr old, normal baseline erectile function, and willing to participate in early erectile dysfunction (ED) therapy. Patients were followed up to 2 yr.

INTERVENTION

Patients underwent UNS RP and ED therapy starting at 6 wk: oral prostaglandin type-5 (PDE5) inhibitor, vacuum erection device (VED), and intracavernosal injection therapy. In the SNG group, a plastic surgeon performed the procedure at the time of RP.

MEASUREMENTS

The ability to have an erection suitable for intercourse with or without a PDE5 inhibitor at 2 yr. The hypothesis was that SNG would result in a 60% potency rate compared to 40% for controls (80% power, 5% two-way significance).

RESULTS AND LIMITATIONS

The trial planned to enroll 200 patients, but an interim analysis at 107 patients met criteria for futility and the trial was closed. For patients completing the protocol to 2 yr, potency was recovered in 32 of 45 (71%) of SNG and 14 of 21 (67%) of controls (p=0.777). By intent-to-treat analysis, potency recovered in 32 of 66 (48.5%) of SNG and 14 of 41 (34%) of controls (p=0.271). No differences were seen in time to potency or quality of life scores for ED and urinary function. Limitations included slower-than-expected accrual and poor compliance with ED therapy: <65% for VED and <40% for injections.

CONCLUSIONS

The addition of SNG to a UNS RP did not improve potency at 2 yr following surgery.

TRIAL REGISTRATION

ClinicalTrials.gov, Identifier: NCT00080808, http://www.clinicaltrials.gov/ct2/show/NCT00080808?term=NCT00080808&rank=1.

Recovery of erectile function after unilateral and bilateral cavernous nerve interposition grafting during radical pelvic surgery

PURPOSE

The use of cavernous nerve interposition grafting to preserve erectile function in men who require neurovascular bundle resection for cancer control is controversial. We report outcomes and predictors of cavernous nerve interposition grafting in men undergoing unilateral grafting during radical prostatectomy or bilateral grafting during radical cystectomy and prostatectomy with autologous nerve grafts.

MATERIALS AND METHODS

We retrospectively reviewed the electronic records of 36 patients who underwent cavernous nerve interposition grafting between 2003 and 2006. Postoperatively erectile function was assessed with the International Index of Erectile Function 15-item questionnaire. Predictors of potency, including age at surgery, time since surgery and prostate specific antigen at surgery, were assessed by univariate analysis.

RESULTS

A total of 33 patients (92% response rate) were followed for a median of 32, 25 and 11 months after bilateral grafting during radical cystectomy (10), unilateral grafting during radical prostatectomy (20), and bilateral grafting during radical cystectomy and prostatectomy (3), respectively. The rate of potency, defined as the ability to attain and maintain erection sufficient for penetration at least 50% of the time with or without phosphodiesterase-5 inhibitors, was 31% (5 of 13 men) for unilateral grafts, 38% (5 of 16) for bilateral grafts and 30% (3 of 10) for bilateral grafts during radical cystectomy. Age at surgery was the only significant determinant of potency and it showed an inverse relationship in the bilateral nerve graft group (p = 0.02).

CONCLUSIONS

Cavernous nerve interposition grafting appears to have a role in the recovery of erectile function. To our knowledge this study represents the largest series of cavernous nerve interposition grafting during cystectomy and it suggests that this should be considered during bilateral neurovascular bundle resection.

Utility of a herpes oncolytic virus for the detection of neural invasion by cancer

Prostate, pancreatic, and head and neck carcinomas have a high propensity to invade nerves. Surgical resection is a treatment modality for these patients, but it may incur significant deficits. The development of an imaging method able to detect neural invasion (NI) by cancer cells may guide surgical resection and facilitate preservation of normal nerves. We describe an imaging method for the detection of NI using a herpes simplex virus, NV1066, carrying tyrosine kinase and enhanced green fluorescent protein (eGFP). Infection of pancreatic (MiaPaCa2), prostate (PC3 and DU145), and adenoid cystic carcinoma (ACC3) cell lines with NV1066 induced a high expression of eGFP in vitro. An in vivo murine model of NI was established by implanting tumors into the sciatic nerves of nude mice. Nerves were then injected with NV1066, and infection was confirmed by polymerase chain reaction. Positron emission tomography with [(18)F]-2'-fluoro-2'-deoxyarabinofuranosyl-5-ethyluracil performed showed significantly higher uptake in NI than in control animals. Intraoperative fluorescent stereoscopic imaging revealed eGFP signal in NI treated with NV1066. These findings show that NV1066 may be an imaging method to enhance the detection of nerves infiltrated by cancer cells. This method may improve the diagnosis and treatment of patients with neurotrophic cancers by reducing injury to normal nerves and facilitating identification of infiltrated nerves requiring resection.

Modified technique for neurovascular bundle preservation during radical prostatectomy: association between technique and recovery of erectile function

OBJECTIVES

To prospectively evaluate whether a modified surgical technique for neurovascular bundle (NVB) preservation during radical prostatectomy (RP) is associated with an improvement in erectile function (EF) recovery after RP.

PATIENTS AND METHODS

Data from patients treated before technique modification was used to create a predictive model for EF at 6 months after RP using age, date of surgery, and nerve sparing (none vs unilateral vs bilateral) as predictors for patients who received the modified technique (MT) to estimate the expected outcomes had they received the standard technique (ST), and compared these with actual outcomes. In the MT, the neurovascular bundle (NVB) is completely mobilized off the prostate from the apex to above the seminal vesicles including incision of Denonvilliers' fascia before urethral division and mobilization of the prostate off the rectum.

RESULTS

Of 372 patients with evaluable data, 275 (74%) underwent the ST from 1 January 2001 to 31 December 2004 and 97 (26%) underwent the MT from 1 January 2005 to 30 May 2006. Sixty-five of 97 patients (67%) receiving the MT had EF recovery at 6 months, whereas the expected probability of 6-month recovery of EF, had they received the ST, was 45%. The absolute improvement in EF recovery attributable to the MT was 22% (95% confidence interval 5-40%; P = 0.013).

CONCLUSIONS

Technical modifications to NVB preservation during RP were associated with improved rates of EF recovery.