Association of hospital volume with perioperative and oncological outcomes of robot-assisted laparoscopic radical prostatectomy: a retrospective multicenter cohort study

Radical prostatectomy is one of the treatment options for localized prostate cancer; robot-assisted radical prostatectomy (RARP) has been widely used in Japan because it is associated with better perioperative outcomes than laparoscopic radical prostatectomy (LRP) and radical retropubic prostatectomy (RRP) [1, 2]. In Japan, there are only a few high-volume centers in which more than 100 cases per year of RARP are performed. Although perioperative outcomes of open radical prostatectomy in high-volume centers and the association between the hospital volume and outcomes have been reported [3, 4], the relationships among hospital volume, biochemical recurrence, and urinary continence are poorly understood. In this study, we investigated the association of hospital volume with perioperative and oncological outcomes in patients treated with RARP.

In this study, through the analysis of long-term data including the biochemical recurrence failure in patients who underwent RARP, we analyzed the clinical outcomes of patients treated at high- and non-high-volume hospitals. Although the non-high-volume hospitals showed a longer console time and more blood loss, the oncological and short-term incontinence outcomes were comparable to that of the high-volume hospitals.

PSA persistence rate in high-volume hospitals was lower than that in non-high-volume hospitals. Bianchi et al. [5] showed that PSA persistence (PSA ≥ 0.1 ng/ml) 6 weeks after radical prostatectomy and PLND were independent predictors of both clinical recurrence and cancer-specific mortality in patients with lymph node invasion. Although we did not find a correlation between PSA persistence and long-term prognosis, PSA persistence may be related to surgical quality.

Previously, only a few studies have analyzed the relationship between hospital volume and RARP outcomes. Budaus et al. [6] reported the relationship between surgeon volume and minimally invasive surgery, including RARP, for the first time. Hirasawa et al. [7] showed that hospital volume is a significant risk factor for perioperative complications. Further, in a study by Xia et al. [8] a higher hospital volume was associated with lower odds of conversion to open surgery, prolonged length of stay, 30-day readmission, and positive surgical margins. All reports suggest that high-volume hospitals have better perioperative outcomes relative to low-volume hospitals. However, these reports have often been analyzed using a national database. Therefore, the observation period was relatively short, and there was little information about recurrence and postoperative complications, such as urinary incontinence. There were some reports about the relationships between hospital volume, oncological outcomes, and urinary complications for open radical prostatectomy. Ellison et al. [9] reported an increased risk of adjuvant therapy with medium- and low- versus high-volume hospitals about RRP. Furthermore, Begg et al. [10] reported that an increased hospital volume was related to reduced rates of postoperative and late urinary complications but not to reduced rates of long-term incontinence about RRP. However, the relationships among hospital volume, biochemical recurrence, and urinary continence of RARP are poorly understood. Therefore, the current study is a valuable report showing these outcomes.

Conventionally, RARP is considered to have a short learning curve. Patel et al. [11] reported a learning curve of approximately 20–25 cases. However, we found that the learning curve is individual-dependent, and the RARP requires more experience to achieve desirable results in practice. Slusarenco et al. [12] reported that the median operative time decreased after the 88th case. Similarly, Doumerc et al. [13] reported that 110 cases would be required to achieve an operative time of 180 min. We investigated the console time in the first 100 and after 100 cases in both the study groups, and found no significant difference in the high-volume hospitals. Hence, the console time in high-volume hospitals is stable from the early stages of introduction, suggesting that the learning curve of high-volume hospitals may be shorter than that of non-high-volume hospitals. Wang et al. [14] reported that the perioperative outcomes, after adding a newly trained surgeon to a high-volume hospital, were not compromised by the learning curve. We investigated the number of surgeons per hospital and the surgeon’s experience with RARP as shown in Table 1. This analysis suggested that non-high-volume hospitals also had experienced surgeons, comparable to those in high-volume hospitals. However, the number of cases that each surgeon performed and experienced with LRP was not included in this study. We must consider the presence of an expert in a high-volume hospital. For surgeons trained in 200–300 LRP procedures, the median operative time for RARP rapidly reduced, and the learning curve was 20 cases [15]. Therefore, further studies are required with consideration of the surgeon’s volume and experience in such analysis.

This study had some limitations. First, the data were collected from only eight institutions and may have caused a selection bias. Therefore, further studies with data from a large number of institutions need to be conducted. Second, this study alone could not determine whether the RARP should be centralized. For example, the initiation of a quality assurance program in London could improve urinary continence 3 months post-surgery [16]. In Japan, Hirasawa et al. [7] reported that surgeon volume was a significant risk factor for perioperative complications. Here, the authors conducted the study using data of RARP performed between 2012 and 2013. Subsequently, the RARP has been frequently implemented in Japan. Additionally, according to the guidelines to start RARP in Japan, the first few operations at each hospital must be proctored by certified experienced surgeons. The proctoring system in Japan may be attributed, in part, to comparable outcomes relevant to the quality measurement of RARP (e.g., oncological outcomes, early continence recovery, and complication rates) between high-volume and non-high-volume hospitals in our study.

The present study demonstrated that a higher hospital volume was significantly associated with shorter console time and less estimated blood loss, suggesting an association between the hospital volume and learning curves. However, surgical quality appears to be comparable between the high- and non-high-volume hospitals in terms of surgical complications, oncological outcomes, and early continence recovery.