Neuroanatomic basis for traction-free preservation of the neural hammock during athermal robotic radical prostatectomy

Correlation between FA and ADC, number and length of the periprostatic neurovascular fibers

PURPOSE

Our aim was to explore the relation between FA and ADC, number and length of the periprostatic neurovascular fibers (PNF) by means of 1.5 T Diffusion Tensor Imaging (DTI) imaging through a multivariate linear regression analysis model.

METHODS

For this retrospective study, 56 patients (mean age 63.5 years), who underwent 1.5-T prostate MRI, including DTI, were enrolled between October 2014 and December 2018. Multivariate regression analysis was performed to evaluate the statistically significant correlation between FA values (dependent variable) and ADC, the number and the length of PNF (independent variables), if p-value <0.05. A value of 0.5 indicated poor agreement; 0.5-0.75, moderate agreement; 0.75-0.9, good agreement; 0.61-0.80, good agreement; and 0.9-1.00, excellent agreement.

RESULTS

The overall fit of the multivariate regression model was excellent, with R² value of 0.9445 (R² adjusted 0.9412; p < 0.0001). Multivariate linear regression analysis showed a statistically significant correlation (p < 0.05) for all the three independent variables. The r partial value was -0.9612 for ADC values (p < 0.0001), suggesting a strong negative correlation, 0.4317 for the number of fiber tracts (p < 0.001), suggesting a moderate positive correlation, and -0.306 for the length of the fiber tracts (p < 0.05), suggesting a weak negative correlation.

CONCLUSIONS

Our multivariate linear regression model has demonstrated a statistically significant correlation between FA values of PNF with other DTI parameters, in particular with ADC.

Depiction of periprostatic nerve fibers by means of 1.5 T diffusion tensor imaging

PURPOSE

The knowledge of periprostatic nerve fiber (pNF) is still incomplete by means of conventional MRI. The purpose of our study was to demonstrate if DTI imaging is able to depict anatomical features of pNF.

METHODS

For this retrospective study, fifty-six patients (mean age 63.5 years), who underwent 1.5-T prostate MRI, including 32 directions DTI, were enrolled between October 2014 and December 2018. ANOVA test and Student's t-test were performed between the mean values of the number, FA values, and fiber length of pNF between base and mid-gland, mid-gland and apex, base and apex, right and left side, and anterior and posterior face of the prostate. A qualitative analysis was performed to detect the main orientation of pNF through a colorimetric 3D tractographic reconstruction.

RESULTS

The number of pNF showed a decrease from the base (322) to mid-gland (248) and apex (75) (p < 0.05). The FA values were higher at base and mid-gland (0.435 and 0.456) compared to the apex (0.313) (p < 0.05). The length of pNF was higher at apex (13.4 mm) compared to base (11.5 mm) and mid-gland (11.7 mm) (p < 0.05). The number of pNF was higher on the posterior face compared to the anterior face at base (186 vs 137), (p < 0.001). The FA values were higher on the posterior face compared to the anterior face at base (0.452 vs 0.417), mid-gland (0.483 vs 0.429), and apex (0.42 vs 0.382), (p < 0.05). The length of the pNF was higher in the posterior (14.7 mm) than in the anterior face (12 mm) at apex (p < 0.001). The main orientation of pNF was longitudinal in all patients (56/56, 100%).

CONCLUSIONS

DTI imaging has been demonstrated able to depict anatomical features of pNF.

cAMP-dependent post-translational modification of neuronal nitric oxide synthase neuroprotects penile erection in rats

OBJECTIVES

To evaluate neuronal nitric oxide (NO) synthase (nNOS) phosphorylation, nNOS uncoupling, and oxidative stress in the penis and major pelvic ganglia (MPG), before and after the administration of the cAMP-dependent protein kinase A (PKA) agonist colforsin in a rat model of bilateral cavernous nerve injury (BCNI),which mimics nerve injury after prostatectomy.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were divided into BCNI and sham-operated groups. Each group included two subgroups: vehicle and colforsin (0.1 mg/kg/day i.p.). After 3 days, erectile function (intracavernosal pressure) was measured and penis and MPG were collected for molecular analyses of phospho (P)-nNOS (Ser-1412 and Ser-847), total nNOS, nNOS uncoupling, binding of protein inhibitor of nNOS (PIN) to nNOS, gp91^phox subunit of NADPH oxidase, active caspase 3, PKA catalytic subunit α (PKA-Cα; by Western blot) and oxidative stress (hydrogen peroxide [H₂ O₂ ] and superoxide by Western blot and microdialysis method).

RESULTS

Erectile function was decreased 3 days after BCNI and normalized by colforsin. nNOS phosphorylation on both positive (Ser-1412) and negative (Ser-847) regulatory sites, and nNOS uncoupling, were increased after BCNI in the penis and MPG, and normalized by colforsin. H₂ O₂ and total reactive oxygen species production were increased in the penis after BCNI and normalized by colforsin. Protein expression of gp91^phox was increased in the MPG after BCNI and was normalized by colforsin treatment. Binding of PIN to nNOS was increased in the penis after BCNI and was normalized by colforsin treatment. Protein expression of active Caspase 3 was increased in the MPG after BCNI and was normalized by colforsin treatment. Protein expression of PKA-Cα was decreased in the penis after BCNI and normalized by colforsin.

CONCLUSION

Collectively, BCNI impairs nNOS function in the penis and MPG by mechanisms involving its phosphorylation and uncoupling in association with increased oxidative stress, resulting in erectile dysfunction. PKA activation by colforsin reverses these molecular changes and preserves penile erection in the face of BCNI.

Robotic-assisted radical prostatectomy learning curve for experienced laparoscopic surgeons: does it really exist?

Background

Robotic-assisted radical prostatectomy (RALP) is a minimally invasive procedure that could have a reduced learning curve for unfamiliar laparoscopic surgeon. However, there are no consensuses regarding the impact of previous laparoscopic experience on the learning curve of RALP. We report on a functional and perioperative outcome comparison between our initial 60 cases of RALP and last 60 cases of laparoscopic radical prostatectomy (LRP), performed by three experienced laparoscopic surgeons with a 200+LRP cases experience.

Materials and Methods

Between January 2010 and September 2013, a total of 60 consecutive patients who have undergone RALP were prospectively evaluated and compared to the last 60 cases of LRP. Data included demographic data, operative duration, blood loss, transfusion rate, positive surgical margins, hospital stay, complications and potency and continence rates.

Results

The mean operative time and blood loss were higher in RALP (236 versus 153 minutes, p<0.001 and 245.6 versus 202ml p<0.001). Potency rates at 6 months were higher in RALP (70% versus 50% p=0.02). Positive surgical margins were also higher in RALP (31.6% versus 12.5%, p=0.01). Continence rates at 6 months were similar (93.3% versus 89.3% p=0.43). Patient’s age, complication rates and length of hospital stay were similar for both groups.

Conclusions

Experienced laparoscopic surgeons (ELS) present a learning curve for RALP only demonstrated by longer operative time and clinically insignificant blood loss. Our initial results demonstrated similar perioperative and functional outcomes for both approaches. ELS were able to achieve satisfactory oncological and functional results during the learning curve period for RALP.

Novel methods for mapping the cavernous nerves during radical prostatectomy

The cavernous nerves, which course along the surface of the prostate gland, are responsible for erectile function. During radical prostatectomy, urologists are challenged in preserving these nerves and their function. Cavernous nerves are microscopic and show variable location in different patients; therefore, postoperative sexual potency rates are widely variable following radical prostatectomy. A variety of technologies, including electrical and optical nerve stimulation, dye-based optical fluorescence and microscopy, spectroscopy, ultrasound and magnetic resonance imaging have all been used to study cavernous nerve anatomy and physiology, and some of these methods are also potential intraoperative methods for identifying and preserving cavernous nerves. However, all of these technologies have inherent limitations, including slow or inconsistent nerve responses, poor image resolution, shallow image depth, slow image acquisition times and/or safety concerns. New and emerging technologies, as well as multimodal approaches combining existing methods, hold promise for improved postoperative sexual outcomes and patient quality of life following radical prostatectomy.

Newer concepts in neural anatomy and neurovascular preservation in robotic radical prostatectomy

With more than 60% of radical prostatectomies being performed robotically, robotic-assisted laparoscopic prostatectomy (RALP) has largely replaced the open and laparoscopic approaches and has become the standard of care surgical treatment option for localized prostate cancer in the United States. Accomplishing negative surgical margins while preserving functional outcomes of sexual function and continence play a significant role in determining the success of surgical intervention, particularly since the advent of nerve-sparing (NS) robotic prostatectomy. Recent evidence suggests that NS surgery improves continence in addition to sexual function. In this review, we describe the neuroanatomical concepts and recent developments in the NS technique of RALP with a view to improving the “trifecta” outcomes.

Robot-assisted radical prostatectomy: inching toward gold standard

Robot-assisted radical prostatectomy (RARP) offers excellent and lasting oncologic control. Technical refinements in apical dissection, such as the retroapical approach of synchronous urethral transection, and adoption of real-time frozen section analysis of the excised prostate during RARP have substantially reduced positive surgical margin rates, particularly in high-risk disease patients. Furthermore, precision offered by the robotic platform and technical evolution of radical prostatectomy, including enhanced nerve sparing (veil), have led to improved potency and continence outcomes as well as better safety profile in patients undergoing surgical therapy for prostate cancer.

Advances in Robotic-Assisted Radical Prostatectomy over Time

Since the introduction of robot-assisted radical prostatectomy (RALP), robotics has become increasingly more commonplace in the armamentarium of the urologic surgeon. Robotic utilization has exploded across surgical disciplines well beyond the fields of urology and prostate surgery. The literature detailing technical steps, comparison of large surgical series, and even robotically focused randomized control trials are available for review. RALP, the first robot-assisted surgical procedure to achieve widespread use, has recently become the primary approach for the surgical management of localized prostate cancer. As a result, surgeons are constantly trying to refine and improve upon current technical aspects of the operation. Recent areas of published modifications include bladder neck anastomosis and reconstruction, bladder drainage, nerve sparing approaches and techniques, and perioperative and postoperative management including penile rehabilitation. In this review, we summarize recent advances in perioperative management and surgical technique for RALP.

Robot-assisted radical prostatectomy: a case series of the first 100 patients--constitutional introduction and implementation on the basis of comprehensive department of minimal invasive surgery center

BACKGROUND

Although a very small number of Japanese hospitals had been performing robotic surgery before 2011, the number now using it is increasing rapidly due to the application of health insurance to robotic surgery for prostate cancer (PCa) since April, 2012. We report our initial experience of treating 100 patients by robot-assisted radical prostatectomy (RARP) with a focus on constitutional introduction and implementation based on minimal invasive surgery center (MISC) and patient outcomes.

METHODS

The MISC involved all of the hospital sections related to robotic surgery including four surgery departments, anesthesiology, operating room nurses, medical engineers. The data were prospectively collected from the first 100 consecutive patients who underwent RARP under supervision of MISC for localized PCa from October 2010 to December 2012.

RESULTS

During the period of our initial 100 cases of RARP, the gynecology, respiratory and digestive surgery departments performed initial cases of 20, 33 and 23 robotic surgeries under control of MISC. Peri-operative complications in RARP appeared to be minimal with no cases of intra-operative open conversion. The positive surgical margin rate was 19% for the entire series. At the median follow-up time of 11.9 months, 91% of patients had undetectable PSA levels, and 76% of patients were not using pads. Sequential urinary functional data indicated a significant beneficial effect on lower urinary tract symptoms beyond cancer control over a period of several months. Although the pre-operative potent patient number was small, the transitions of constant potency recovery at precise time points were shown according to different nerve sparing procedures.

CONCLUSIONS

This is the first report of an initial 100 RARP cases that were implemented using the constitutional framework of an academic institution. The MISC is providing immeasurable benefits from the aspects of patient safety and education for the robotic surgical team. RARP is a safe and efficient method for achieving PCa control together with functional preservation, even during the initial trial for this procedure.

Improving time to continence after robot-assisted laparoscopic prostatectomy: augmentation of the total anatomic reconstruction technique by adding dynamic detrusor cuff trigonoplasty and suprapubic tube placement

After robot-assisted laparoscopic prostatectomy, total anatomic reconstruction (TR) with the additions of a circumapical urethral dissection, a dynamic detrusor cuff trigonoplasty, and placement of a suprapubic catheter was performed in 49 patients from June to July 2012. Continence at 6 weeks after catheter removal was assessed for an initial group of 23 patients, and also at 2 weeks in an additional 26 patients who most recently had undergone surgery. Follow-up appointments and telephone interviews were used to assess pad use and continence. Of the initial 23 patients receiving the modified TR, 60.9% had 0 pad use at 6 weeks. By 2 weeks, 65.4% of the most recent 26 patients operated on achieved continence with 0-1 pad use. Preservation and reconstruction of the pelvic floor and supporting bladder structures leads to an earlier return of continence. These key steps need to be validated and confirmed in larger and randomized trials.

Diffusion tensor magnetic resonance tractography of the prostate: feasibility for mapping periprostatic fibers

OBJECTIVE

To evaluate the feasibility of diffusion tensor imaging (DTI) tractography of the prostate for mapping of periprostatic neurovascular anatomy.

METHODS

Eight men with prostate cancer scheduled to undergo nerve-sparing robot-assisted radical prostatectomy (RARP) underwent endorectal multiparametric magnetic resonance imaging (MRI) of the prostate with DTI. Tract mapping was accomplished by positioning spherical regions of interest contiguously along the prostatic capsule at the prostatic apex, midgland, and base.

RESULTS

DTI tractography of the prostate effectively visualized periprostatic fiber tract anatomy. There was no significant correlation between total tract number and prostate size, however (Spearman's coefficient = 0.33, P = .42). Variation in tract distribution existed. The total fiber mass was highest in the lower prostate hemisphere at the base of the prostate (mean = 36.9 vs 21.1, P = .0004) and in the upper hemisphere at the apex (mean = 41.6 vs 57.9, P = .006).

CONCLUSION

DTI tractography successfully visualized fiber tracts around the prostate. Gold standard anatomic correlation is needed.

Nerve mapping for prostatectomies: novel technologies under development

Prostatic neuroanatomy is difficult to visualize intraoperatively and can be extremely variable. Damage to these nerves during prostatectomies may lead to postoperative complications such as erectile dysfunction and incontinence. This review aims to discuss the prostatic neuroanatomy, sites of potential nerve damage during a prostatectomy, and nerve-mapping technologies being developed to prevent neural injury. These technologies include stimulation, dyes, and direct visualization. Nerve stimulation works by testing an area and observing a physiologic response but is limited by the long half-life for an erectile response; examples include CaverMap, ProPep, and optical nerve stimulation. Few nerve dyes have been approved by the Food and Drug Administration (FDA) because of the extensive testing required; examples of nerve dyes include compounds from Avelas and General Electric, fluorescent cholera toxin subunit B, indocyanine green, fluorescent inactivated herpes simplex 2, and Fluoro-Gold. Direct visualization techniques have a simpler FDA approval process; examples include optical coherence tomography, multiphoton microscopy, ultrasound, coherent anti-Stokes Raman scattering. Many researchers are developing several novel technologies that can be categorized as stimulation based, dye-based, or direct visualization. As of yet, none has shown clear evidence to improve surgical outcomes and consequently lack wide adoption. Further development of these technologies may lead to improved complication rates after prostatectomies. Clinically, some technologies have demonstrated utility in predicting the development of complications. By using that information, more aggressive rehabilitation programs may lead to improved long-term function. These technologies can also be applied for research to improve our knowledge of the neuroanatomy and physiology of erection and incontinence.

Optimizing radical prostatectomy for the early recovery of urinary continence

Radical prostatectomy remains the gold-standard treatment for clinically localized prostate cancer. Although cancer control is the primary goal, secondary outcomes such as continence recovery are of great importance to patients. Thus, it is a challenge for prostate cancer surgeons to optimize continence outcomes without compromising oncologic results. Many high-volume surgeons have demonstrated excellent long-term continence rates in their patients, but early continence is variable and less than ideal even in expert hands. A plethora of individual technical maneuvers exist to optimize early recovery of continence, but as yet there is no composite technique that incorporates the relevant anatomic principles of minimizing damage to the urinary sphincters and their nerves, maximizing functional urethral length, creating a secure and watertight vesicourethral anastomosis, providing circumferential fascioligamentous support to the anastomosis and external sphincter, and ameliorating postoperative bladder descent. Our ten-step approach to collating these individual maneuvers into a unified technique could be used by surgeons to obtain the best possible early recovery of urinary control for their patients, without risking their oncologic outcomes.

Pathological outcomes and strategies to achieve optimal cancer control during robotic radical prostatectomy in Asian-Indian men

INTRODUCTION AND OBJECTIVES

There is a paucity of information in the literature about the characteristics of prostate cancer in the Asian-Indian population. We wanted to evaluate the oncological outcomes of Asian-Indians and Caucasians. We also derived a nomogram for prediction of extraprostatic extension (EPE) and presented biochemical recurrence (BCR) rates in the Asian-Indian population.

MATERIALS AND METHODS

A total of 2367 D'Amico low-risk patients underwent robotic-assisted radical prostatectomy (RARP) for clinically localized prostate cancer between January 2005 and July 2010 by a single surgeon. Of these 56 (2.4%) patients were Asian-Indians and 2025 were Caucasians (85.6%). Univariate and multivariate models were created for predicting EPE. A multivariate logistic regression model was used to develop a predictive nomogram. BCR was defined as a prostate-specific antigen ≥0.2 at any postoperative time point. Kaplan-Meier survival analysis was used to investigate BCR rates.

RESULTS

A significantly greater percentage of Asian-Indians compared to Caucasians had EPE (32.3 vs. 16.5; P = 0.01). In multivariate analysis adjusted for significant variables from univariate analyses, Asian-Indian race (P = 0.028), age (P = 0.050), maximum percentage cancer on biopsy (P < 0.001), and pathology prostate weight (P = 0.047) were independent predictors of EPE. Kaplan-Meier analysis demonstrated BCR free rates of 94.6% and 95.4%, for Asian-Indians and Caucasians, respectively, at a median follow-up of 16 months (range 2-70 months). There was no statistically significant difference in BCR rates across the two cohorts (log-rank P-value = 0.405).

CONCLUSIONS

This study highlights that while Asian-Indians have more advanced cancer variables, their risk of BCR after surgery is similar to Caucasian patients. Further work is required to better understand the social, genetic and environmental factors that affect the biology of prostate cancer in men of Asian-Indian descent.

Anatomical grades of nerve sparing: a risk-stratified approach to neural-hammock sparing during robot-assisted radical prostatectomy (RARP)

OBJECTIVES

• To report the potency and oncological outcomes of patients undergoing robot-assisted radical prostatectomy (RARP) using a risk-stratified approach based on layers of periprostatic fascial dissection. • We also describe the surgical technique of complete hammock preservation or nerve sparing grade 1.

PATIENTS AND METHODS

• This is a retrospective study of 2317 patients who had robotic prostatectomy by a single surgeon at a single institution between January 2005 and June 2010. • Included patients were those with ≥ 1 year of follow-up and who were potent preoperatively, defined as having a sexual health inventory for men (SHIM) questionnaire score of >21; thus, the final number of patients in the study cohort was 1263. • Patients were categorized pre-operatively by a risk-stratified approach into risk grades 1-4, where risk grade 1 patients received nerve-sparing grade 1 or complete hammock preservation and so on for risk grades 2-4, as long as intraoperative findings permitted the planned nerve sparing. • We considered return to sexual function post-operatively by two criteria: i) ability to have successful intercourse (score of ≥ 4 on question 2 of the SHIM) and ii) SHIM >21 or return to baseline sexual function.

RESULTS

• There was a significant difference across different NS grades in terms of the percentages of patients who had intercourse and returned to baseline sexual function (P < 0.001), with those that underwent NS grade 1 having the highest rates (90.9% and 81.7%) as compared to NS grades 2 (81.4% and 74.3%), 3 (73.5% and 66.1%), and 4 (62% and 54.5%). • The overall positive surgical margin (PSM) rates for patients with NS grades 1, 2, 3, and 4 were 9.9%, 8.1%, 7.2%, and 8.7%, respectively (P = 0.636). • The extraprostatic extension rates were 11.6%, 14.3%, 29.3%, and 36.2%, respectively (P < 0.001). • Similarly, in patients younger than 60, intercourse and return to baseline sexual function rates were 94.9% and 84.3% for NS grade 1 as compared to 85.5% and 77.2% for NS grades 2, 76.9% and 69% for NS grades 3, and 64.8% and 57.7% for NS Grade 4 (P < 0.001).

CONCLUSIONS

• The risk-stratified approach and anatomical technique of neural-hammock sparing described in the present manuscript was effective in improving potency outcomes of patients without compromising cancer control. • Patients with greater degrees of NS had higher rates of intercourse and return to baseline sexual function without an increase in PSM rates.