This current study is one of the largest retrospective studies to focus on sp-pRARP using the da Vinci XI system, as well as the first to focus on the sp-pRARP learning curve. Open perineal RP was abandoned and replaced by the retropubic approach because of the limited perineal anatomy, high incidence of complications, and the advent of minimally invasive laparoscopic surgeries. Robotic surgical platforms have brought an improved three-dimensional view of the surgical field and flexible robotic instrumentation allowing surgeons to accomplish complex maneuvers in smaller spaces thus creating opportunities to develop novel methods such as ours.
Abdominal/pelvic surgical history, such as inguinal hernia repair (IHR), have proposed significant challenges for robot-assisted RP due to the adhesions and distortion of anatomic planes(15), and obscuring the pelvic lymph node dissection (PLND)(16). The adhesions in the inguinal area induced by IHR would make it difficult to place trocars in the appropriate position during retropubic RP, lengthening the trocars placement time and the prostatectomy time(17). The perineal approach offers another surgical option when faced with a patient with extensive prior abdomino-pelvic surgical history, eliminating the concern of adhesiolysis. In our study, there was no statistically significant difference in terms of the parameters between patients with and without a history of IHR (Supplement Table 4). The results might be explained by the small number of patients with IHR history, but we could still presume that sp-pRARP might be an alternative for individuals who were not candidates for retropubic RARP.
Bilateral pelvic lymph node dissection (PLND) is a critical procedure that should not be overlooked and is challenging to perform in the sp-pRARP. The staging information gained from PLND comes at the risk of prolonged surgical times and lymphorrhagia. According to the American Association of Urology and European Association of Urology (18, 19), PLND should be performed when the predicted probability of lymph node metastasis is greater than 2% or greater than 5%, and patients with low risk do not require PLND. Ramirez et al.(20) firstly described the technique of PLND in sp-pRARP on the da Vinci SP platform. Tugcu et al.(21) also introduced the Tugcu-Bakirkoy technique to complete the same procedure on the da Vinci XI system. The majority of patients in our series had low to intermediate risk cancers, and preoperative PET/CT examination was used for patients who had a relatively high risk of lymph node metastasis. Due to the unfamiliarity and inherent difficulties of PLND in sp-pRARP, and the low possibility of lymph node metastases shown by PET/CT, PLND was not performed in this investigation.
PSMs have been identified as an independent predictor of biochemical recurrence (BCR), and may lead to subsequent adjuvant or salvage therapies (X-Ray therapy with or without androgen deprivation therapy). According to a multicenter study, the overall PSM rate for RARP was 13.6%, while the PSM rates for the pT2 and pT3 stages were 9.45% and 37.2%, respectively(22). The PSM rate of p-RARP ranged from 8.4–65.4% in known case series(4–7). In this study, 5 (10%) patients experienced a PSM. Only one patient had a biochemical recurrence during our short follow-up period and required salvage radiotherapy. Additional longitudinal follow-up analyses may reveal more complete oncologic outcomes in the future.
Continence status is an important functional outcome parameter after RARP. Meta-analysis have supported that RARP is associated with excellent 12-month continence, with urine continence recovery rates ranging between 84% and 97%(23). Twelve months following surgery, our results indicate a 97.7% recovery rate for postoperative continence. We feel the post sp-pRARP continence recovery may be improved because the perineal approach allowed for less injury to the auxiliary pudendal arteries and dorsal veins, as well as improved preservation of the endopelvic fascia.
As anticipated when adopting a new technique, the incidence of complications was higher than expected but fortunately not severe. The risk of carbon dioxide (CO2) embolism, although has a low incidence, has an extremely high fatality rate in laparoscopy(24). Bao et al.(25) reported one case of CO2 embolism during laparoscopic RP. But in the reported RARP case series, this severe complication has not been reported. In our study, two patients experienced ARDS due to CO2 embolization, which was most likely caused by the intelligent pneumoperitoneum Airseal® insufflator. The insufflator maintained a steady pressure by a continuous infusion of CO2, potentially preventing air leaks during specimen collection or instrument/lens changes that could disrupt the flow of the process. During a prolonged procedure, the charged CO2 could be absorbed in considerable quantities by the surrounding tissue, resulting in CO2 embolism and manifesting as decreased percutaneous oxygen saturation (SpO2) and end-tidal carbon dioxide (ETCO2), hypoxemia, hypercapnia, increased airway resistance, and hemodynamic abnormalities. Therefore, patient's SpO2 changes should be monitored closely throughout the surgical process. In addition, poor wound healing was observed in our study, which might be caused by a relatively large prostate volume and a lengthy operation.
Our research is the first to examine the learning curve of da Vinci Xi sp-pRARP by using the CUSUM method. The CUSUM plot demonstrated that 20-cases was the critical cutoff point for the learning curve of an experienced robotic/laparoscopic surgeon. Moreover, comparisons between the two phases revealed that proficiency had improved significantly in the "late phase". The operating time, docking time, and console time were all noticeably shorter in the "late phase" compared to the "early phase", and the EBL was also noticeably reduced. Although the operation time for sp-pRARP was still significantly longer compared to mp-RARP, our learning curve showed a significant improvement with the accumulation of experience. Due to a greater understanding of the anatomy of the perineal region, surgeons may be able to operate more skillfully and with less damage to the surrounding blood vessels after a certain amount of experience and practice. Regarding continence, the difference was only observed during the initial three months, and it decreased as time passed.
Our study has several limitations. First, the conclusions were derived from a small-sample retrospective study, and potential selection bias may have affected the reliability of the final results. Second, the short follow-up period prevented the conclusion of long-term postoperative functional recovery and oncological outcomes. Although additional research is needed to verify the long-term safety and efficacy of sp-pRARP, it may offer another surgical option to patients with complicated abdominal/pelvic histories.