Subjects

Between May 2011 and February 2013, 219 consecutive patients were recruited for this study, each of whom underwent RALP at Nagoya City University Hospital. The study received approval from our institutional review board (“Robot-assisted laparoscopic radical prostatectomy for prostate cancer”, No. 46-10-0009) and conforms to the provisions of the Declaration of Helsinki. Each patient provided informed consent. The preoperative assessments of all patients included detailed patient histories, clinical examinations, serum prostate-specific antigen (PSA) measurements, biopsy findings, Gleason score measurements, bone scan results, and contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) findings. Baseline demographic clinical staging was conducted according to the TNM staging system (Union Internationale Contre le Cancer, 2002 classification), and only patients with T_1–3N₀M₀ stage cancers were considered for RALP. Patients were divided according to their pathologic prostate weight as follows: group 1, <30 g; group 2, ≥30 g to <50 g; group 3, ≥50 g to <80 g; and group 4, ≥80 g. Preoperative, intraoperative, and postoperative parameters were analyzed. One patient, who required open conversion, was excluded from all statistical analyses.

The procedures were performed by five surgeons with experience in open radical prostatectomy and laparoscopic radical prostatectomy. The entire surgical team underwent 1 week of intensive training at Sukagawa Training Center (Fukushima, Japan), and received surgical practice at the St. Augustin Hospital (Bordeaux, France) and the Yonsei University Severance Hospital (Seoul, Korea).

The following data were collected and reviewed for the present study: patient age, body mass index (BMI), total operating time (including port placement, docking of the robot, dissection, anastomosis, and closure), duration of robotic surgery, duration of anastomosis, estimated blood loss, presence or absence of urinary incontinence (pad usage), duration of postoperative bladder catheterization, intraoperative complications, immediate postoperative complications (appearing within the first month after surgery), long-term complications (appearing after the first postoperative month), TNM staging, and surgical margins status.

Surgical technique

All patients eligible for radical prostatectomy were offered RALP, which was performed using a 4-arm da Vinci-S robotic system (Intuitive Surgical, Sunnyvale, USA). Our technique was based on that used at the Vattikuti Institute (Detroit, USA), combined with the use of diathermy scissors [8]. Previously, we had performed laparoscopic radical prostatectomy using a posterior approach to the seminal vesicle and following the Montsouris method [9]. Therefore, we adopted the same approach for the RALP procedure [10]. Briefly, we used an intraperitoneal approach. The seminal vesicles were dissected first, using a posterior approach. The rectum was retracted in a cephalad dissection by the assistant. The superior peritoneal arch (created by the impression of the Foley balloon) was grasped by the assistant or the third arm of the da Vinci-S and lifted upwards. The monopolar scissors were then used to create a curvilinear incision midway between the anterior rectal wall and the grasped arch. The incision was deepened by blunt dissection through the fibro-alveolar tissue, revealing both vas deferens (VDs). The VDs were dissected free, approximately 3 cm from the prostate, and transected. Blunt dissection of the anterior fibrovascular tissue overlying the seminal vesicles (SVs) was continued laterally. Once the dissection had been completed to the level of the base, blunt medial dissection freed the posterior surface of the SVs. After both SVs were completely dissected, upward traction on both SVs and VDs facilitated an incision into Denonvillier’s fascia, which allowed the posterior dissection to continue to the level of the rectourethralis fibers. Subsequently, dorsal vein control was achieved using 2-0 V-Loc™ on a 37-mm needle (Covidien, Mansfield, USA). The vascular pedicles were clipped with Hem-o-lock (Teleflex, Limerick, USA) to control the posterolateral small vessels when nerve sparing was performed. Thereafter, the prostatectomy was conducted in an almost antegrade fashion, preserving the neurovascular bundles when indicated using a clipless technique [11]. The Rocco suture [12] was also adopted, using 3-0 V-Loc™ on a 26-mm needle (Covidien). Large bladder neck defects were reconstructed using a “fish mouth” or “parachute” technique with anastomosis to the urethral stump, as chosen according to the surgeon’s preference [13]. In the “fish mouth” technique, two interrupted Vicryl sutures (from the 2-o’clock to the 4-o’clock position and from the 8-o’clock to the 10-o’clock position) were placed on the bladder neck, to narrow the diameter of the bladder neck opening until it matched the urethral diameter. Finally, we performed running vesicourethral anastomosis using two 3-0 PDSII (Ethicon Endo-Surgery, Cincinnati, USA) sutures, retightened with Lapra-Ty (Ethicon Endo-Surgery) at the 3- and 9-o’clock positions. Each patient who had an intermediate or high D’Amico risk [14] underwent lymph node dissection. Nerve-sparing surgery was performed for the 43 cases in which unilateral cancer was detected by needle biopsy or the patient expressed a desire for nerve-sparing surgery.

Complications

Intraoperative and postoperative complications were critically assessed and compared across the four prostate weight groups. Postoperative complications were graded according to a system described by Clavien [15]. Following this system, grade I complications include alterations from the ideal postoperative course that are not life threatening and cause no lasting disability. Grade II complications require pharmacological treatment with drugs, blood transfusions, or total parenteral nutrition. Grade III complications require surgical, endoscopic, or radiological intervention. Grade IV complications are life threatening. Grade V is assigned when death results from a complication.

Pathological analysis of specimens

The final Gleason score, degree of positive margins, and seminal vesicle or lymph node involvement were included in histopathological assessments. The specimen’s pathological processing included 4-mm sectioning of the whole gland. The presence of malignant glands in direct contact with the inked surface was defined as constituting positive margins.

Patient follow-up

Follow-up visits were conducted at regular intervals. Follow-up included serial PSA monitoring in addition to assessments of functional outcomes, such as continence and erectile function. The rate of continence was investigated for the 199 patients (91%) who had over 6 months of follow-up data. Patients with urge incontinence were excluded from the follow-up study. Continence was assessed using a questionnaire that was provided 1, 3, and 6 months after RALP. Functional data were prospectively assessed using the Expanded Prostate Cancer Index Composite. Men requiring greater than 0 precautionary pads per day were considered incontinent. Twelve months of follow-up data on incontinence were available for 101 patients (46%).

Statistical analysis

An analysis of variance model was used to compare continuous outcome variables among the groups. Chi-squared and Fisher’s exact tests were used to compare categorical outcome variables. Each significant overall effect was additionally investigated in a post-hoc pairwise comparative analysis that used the Tukey test and Bonferroni-adjusted P values. Two-tailed P values <0.05 were considered statistically significant.

Baseline demographics

Perioperative outcomes

Transfusion rates and mean Foley catheterizations were similar across the four groups (Table 1). The series excluded one open conversion, which resulted from abdominal adhesion and was one of the first 20 cases in the series. Total operation times and robotic times were significantly greater among patients with prostate weights ≥50 g (P < 0.01). Estimated blood loss and anastomosis time tended to be greater in the higher prostate weight group, but the differences were not significant.

Five patients experienced intraoperative complications, including 3 patients with posterior bladder injury, 1 patient with rectal injury, and 1 patient with ileum injury. In all these patients, the injury was repaired during a robotic operation. No association was observed between prostate weight and incidence of intraoperative complications.

Pathological outcomes

All cases among patients with prostates weighing ≥80 g had pathologic stage T2 (Table 1). However, we found no significant differences in rates of positive margins. Although we noted a trend among the pT3 population, it was not statistically significant. Considering all 219 patients, the mean short-term follow-up was 11.5 months. There were no significant differences in follow-up time between the prostate weight groups.

Functional outcomes

In the <30 g, 30–49 g, 50–79 g, and ≥80 g groups, 17 (89.5%), 130 (90.9), 46 (90.2%), and 6 (100%) patients had 1, 3 and 6 months of follow-up data, and were therefore eligible for the questionnaire. At 1, 3 and 6 months, the mean extent of return to baseline urinary function was similar across the groups (Table 2). In the group of patients with prostates weighing ≥50 g, the continence rates tended to be somewhat low at 1 and 3 months; however, the continence rates were similar in all the groups after 6 months. Furthermore, at 12 months, the urinary continence rates were similar in the <30 g, 30–49 g, 50–79 g, and ≥80 g groups, specifically being 87.5%, 87.9%, 87.5%, and 66.7%, respectively. The 12-month continence data included 101 patients overall, comprising 8, 66, 24, and 3 patients in the <30 g, 30–49 g, 50–79 g, and ≥80 g groups, respectively. Incontinence events in these groups were thought to be stress urinary incontinence because patients with urge incontinence had been excluded.

Oncological outcomes

PSA recurrence at 6 months did not differ significantly across the groups.