Initial Experience of Robot-Assisted Partial Nephrectomy Using Hinotori Surgical Robot System: Single Institutional Prospective Assessment of Perioperative Outcomes in 30 Cases

Abstract

Introduction:

Innovation of robotic surgery is still actively growing, and various novel robotic systems are in the process of development. The objective of this study was to assess the perioperative outcomes of robot-assisted partial nephrectomy (RAPN) using the hinotori surgical robot system, a recently developed robot-assisted surgical platform, for patients with small renal tumors.

Methods:

This study prospectively included a total of 30 consecutive patients who were found to have small renal tumors and subsequently underwent RAPN using hinotori between April and November 2022. Major perioperative outcomes in these 30 patients were comprehensively analyzed.

Results:

The median tumor size and R.E.N.A.L. nephrometry score in the 30 patients were 28 and 8 mm, respectively. Of these 30, 25 and 5 received RAPN by intra- and retroperitoneal approaches, respectively. RAPN could be completed in all 30 patients without conversion to nephrectomy or open surgery. The median operative time, time using hinotori, and warm ischemia time were 179, 106, and 13 minutes, respectively. No patient was found to have a positive surgical margin or experienced major perioperative complications, corresponding to Clavien–Dindo 3≤. Achievements of trifecta and margin, ischemia, and complications (MIC) outcomes in this series were 100% and 96.7%, respectively, and median changes in the estimated glomerular filtration rate 1 day and 1 month after RAPN were −20.9% and −11.7%, respectively.

Conclusions:

This is the first study focusing on RAPN using hinotori, which showed favorable perioperative outcomes, considering the findings of trifecta and MIC. Although it will be necessary to investigate the long-term effects of RAPN using hinotori on oncologic and functional outcomes, the present findings strongly suggest that the hinotori surgical robot system could be safely applied to RAPN for patients with small renal tumors.

Introduction

Minimally invasive surgery (MIS) has been revolutionized by the recent introduction of robotic surgery into routine clinical practice, since the robotic system expanded the indications of MIS in cases requiring more complex procedures. This could be achieved by the assistance of several advantageous characteristics, including articulating wrists to achieve multiple degrees of motion, 3-dimensional (3D) visualization, magnified vision, elimination of physiologic tremors, and improved dexterity.¹ In particular, robotic surgery has been widely accepted as a standard approach in a wide variety of surgeries in the field of urology, such as radical prostatectomy, partial nephrectomy, and radical cystectomy.² In Japan as well, most major urologic surgeries have been approved by the health insurance system, resulting in a marked increase in the proportion of urologic surgeries performed using robotic surgical systems.³

For the past two decades, the surgical robot market has been dominated by the da Vinci surgical system (Intuitive Surgical, Inc., Sunnyvale, CA), but the recent expiration of some of the patents associated with da Vinci has promoted the development of novel robotic platforms with different technical refinements.^4

–8 Of these, the hinotori surgical robot system was developed by Medicaroid Corporation (Kobe, Japan), jointly funded by Kawasaki Heavy Industries (Kobe, Japan) and Sysmex Corporation (Kobe, Japan), and has already been introduced into routine clinical practice in Japan.⁸

The hinotori system is characterized by a compact operation arm with eight axes of motion, one more than the da Vinci system, and thus minimizes the interference between the arms. Furthermore, the safety of this surgical platform was shown in a first-in-human trial of robot-assisted radical prostatectomy (RARP) involving 30 prostate cancer patients⁸; however, the utilities of hinotori in other surgeries, including robot-assisted partial nephrectomy (RAPN), have yet to be investigated. Considering these findings, this study analyzed perioperative outcomes in 30 patients with small renal tumors undergoing RAPN using hinotori.

Patients and Methods

Patients

This study prospectively included a total of 30 consecutive patients with small renal tumors who underwent RAPN using hinotori between April and November 2022 at our institution. The design of this study was approved by the Research Ethics Committee of our institution (permission number 21-313) and written informed consent to be involved in this study was obtained from all 30 patients.

Evaluation

All data on clinicopathologic and perioperative findings of the 30 patients were obtained from their electronic medical records at our hospital. According to a previous report, the R.E.N.A.L. nephrometry score, reflecting the tumor complexity in each case,⁹ was analyzed based on contrast-enhanced CT, and postoperative complications were evaluated using the Clavien–Dindo classification system.¹⁰ As a rule, enhanced CT was conducted as routine management 3 days after RAPN to examine whether a postoperative renal artery pseudoaneurysm and/or urinary leakage developed.

In this series, the achievement of trifecta outcomes was defined as the simultaneous fulfillment of three factors as follows: warm ischemia time ≤25 minutes, no positive cancer margin, and no postoperative complications corresponding to grade 3≤ of Clavien–Dindo classification, whereas the margin, ischemia, and complications (MIC) score was also assessed as an alternative strict surrogate, based on the definition of ischemia time <20 minutes in addition to negative surgical margins and no complication corresponding to Clavien–Dindo grade 3≤.¹¹

Surgical procedure

Detailed features of the hinotori surgical robot system were previously reported.⁸ Before RAPN, 3D-reconstructed images of the affected kidney were created based on digital data obtained from enhanced CT in each patient by a CT image analysis system, Synapse Vincent (FUJIFILM Medical Co., Tokyo, Japan), and were directly displayed on the surgeon's cockpit screen using TilePro multi-input display functions during RAPN.

In this series, RAPN was conducted by three cockpit surgeons, who had been certified as proctors for robot-assisted surgery by the Japanese Society of Endourology and Robotics, according to procedures similar to those adopted in our previous series using da Vinci.^12,13 In brief, three trocars for the use of robotic arms and two or three trocars for the assistant's ports, including AirSeal iFS (CONMED Japan KK, Tokyo, Japan), were placed, irrespective of the surgical approach, and the following instruments were used during RAPN: monopolar curved scissors, bipolar fenestrated forceps, and wide needle holder. To evaluate the intrarenal shapes of the tumors and determine the resection line with sufficient margins, intraoperative ultrasound examinations were performed with an ARIETTA 70 probe (Hitachi, Inc., Tokyo, Japan).

The main renal artery on the affected side was subsequently secured at the renal hilar level, and clamped with a Bulldog applied through the assistant port, followed by the resection of tumors, maintaining a secure margin. An inner running suture using 3-0 V-Loc (COVIDIEN Japan, Inc., Tokyo, Japan) was placed to repair the collecting system and large vessels. After early unclamping of the main renal artery, soft coagulation (VIO300D; ERBE Elektromedizin GmbH, Tübingen, Germany) and/or further inside suturing was added, and parenchymal renorrhaphy was performed using 2-0 V-Loc. Finally, a hemostatic agent, Beriplast P Combi-Set Tissue adhesion (CSL Behring, Inc., Tokyo, Japan), was used to cover the sutured renal scar.

Results

Thirty patients, who were found to have small renal tumors and consented to receive RAPN using the hinotori surgical robot system, were prospectively included in this study. Table 1 summarizes baseline clinical parameters of these 30 patients. Since the transperitoneal approach was generally selected at our institution, only five patients underwent RAPN through a retroperitoneal approach because of either a previous history involving major surgeries for abdominal organs or a tumor location at the dorsal renal hilus.

Table 1.

Preoperative Characteristics of 30 Patients Who Underwent Robot-Assisted Partial Nephrectomy Using Hinotori

Male	20 (66.7)
Female	10 (33.3)
Age (years), median (range)	62 (46–84)
Previous history of abdominal surgery (%)	8 (26.7)
Body mass index (kg/m²), median (range)	23.6 (19.7–48.9)
Diabetes mellitus (%)	10 (33.3)
Hypertension (%)	13 (43.3)
Preoperative chronic kidney disease (%)	9 (30.0)
Tumor site (%)
Right	19 (63.3)
Left	11 (36.7)
Clinical T stage (%)
T1a	23 (76.7)
T1b	7 (23.3)
Tumor size (mm), median (range)	28 (8–53)
Hilar tumor (%)	5 (16.7)
Cystic tumor (%)	2 (6.7)
Endophytic tumor (%)	2 (6.7)
R.E.N.A.L. nephrometry score, median (range)	8 (5–10)
Surgical approach (%)
Transperitoneal	25 (83.3)
Retroperitoneal	5 (16.7)

In this series, RAPN using hinotori could be completed in all 30 patients without conversion to nephrectomy or open surgery. In this series, equipment malfunction requiring recovery time for >5 minutes occurred in only one case (3.3%). Major surgical and pathologic outcomes of the 30 patients are presented in Table 2. There was no patient who was pathologically found to have a positive surgical margin or experienced major perioperative complications, corresponding to Clavien–Dindo 3≤, whereas the warm ischemia times in 30 and 29 patients were ≤25 and <20 minutes, respectively. Accordingly, trifecta and MIC outcomes in this series were 100% and 96.7%, respectively.

Table 2.

Surgical and Pathologic Outcomes of 30 Patients Who Underwent Robot-Assisted Partial Nephrectomy Using Hinotori

Operative time (minutes), median (range)	179 (122–268)
Time using robotic system (minutes), median (range)	106 (73–191)
Estimated blood loss (mL), median (range)	39 (5–312)
Warm ischemia time (minutes), median (range)	13 (5–20)
Histologic subtype (%)
Clear cell renal cell carcinoma	25 (83.3)
Other malignancy	4 (13.3)
Benign tumor	1 (3.3)
Positive cancer margins (%)	0 (0.0)
Intraoperative blood transfusion (%)	0 (0.0)
Conversion to open surgery (%)	0 (0.0)
Conversion to nephrectomy (%)	0 (0.0)
Renal artery pseudoaneurysm (%)	0 (0.0)
Urinary leakage (%)	0 (0.0)
Major postoperative complications (Clavien–Dindo 3 or 4)	0 (0.0)
Hospital stay after surgery (days), median (range)	7 (4–23)
Achievement of trifecta (%)	30 (100.0)
Achievement of MIC (%)	29 (96.7)
Change in eGFR (%), median (range)
1 postoperative day	−20.9 (−54.0 to 5.9)
1 postoperative month	−11.7 (−25.6 to 11.8)

eGFR = estimated glomerular filtration rate; MIC = margin, ischemia, and complications.

Discussion

In recent years, particularly after the expiration of several patents associated with the da Vinci in 2019, novel robotic surgical systems have been developed by several companies, and more are currently under active development.^4

–8 Of these, hinotori is the first made-in-Japan surgical robotic system, which consists of three components, such as the da Vinci system, including the patient cart, surgeon's cockpit, and vision unit, but has several characteristics different from da Vinci. For example, the docking-free design of hinotori, which does not require docking of an arm with a port, contributes to provide a large space in a clean field for the surgeons and to protect against collisions between arms outside the body, whereas compact robotic arms with eight axes of motion are mounted in hinotori, designed to realize accurate and minute manipulations.⁸

In 2020, the hinotori surgical robotic system received regulatory approval in Japan, and the use of this system in routine clinical practice has gradually increased in the field of urology. As for the use of hinotori, however, there has been only one study describing the outcomes of a first-in-human trial of RARP,⁸ and no information with respect to other surgeries using hinotori is available. Therefore, this study comprehensively investigated the initial experience with RAPN using hinotori, focusing on perioperative findings in 30 prospectively included patients with small renal tumors.

At our institution, RAPN was initiated in April 2016 immediately after insurance coverage, and a total of 303 patients with small renal tumors had undergone RAPN using da Vinci until March 2022.^12,13 However, since the introduction of the hinotori surgical robot system in April 2022, this system was used for all patients with small renal tumors undergoing RAPN, even those with complex tumors. In fact, 15 patients (50.0%) in this series of RAPN using hinotori had renal tumors corresponding to complex tumors characterized by cT1b, completely endophytic, hilar, and/or cystic tumors.¹⁴ Considering these findings, the characteristics of renal tumors in the included patients in this initial series using hinotori may be similar or even more complex compared with those treated with RAPN using da Vinci in routine clinical practice.

At our institution, only surgeons certified as proctors for robot-assisted surgery have been involved in RAPN as operators, irrespective of the use of da Vinci or hinotori, and none of the surgical steps during RAPN was modified or changed after introducing the hinotori surgical robot system. As a result, RAPN using hinotori could be completed in all the 30 included patients, as preoperatively scheduled, and favorable perioperative outcomes could generally be achieved in this initial series. All 30 patients achieved trifecta outcomes, the most widely accepted key surrogate for effectively conducted PN, and an alternative strictly defined surrogate MIC was accomplished by 29 of the 30 patients.

Furthermore, three cockpit surgeons in this series had experience with RARP using hinotori for only <5 cases before the involvement in RAPN; however, there was no learning curve effect on the initial phase of RAPN using hinotori, characterized by the lack of significant differences of major perioperative outcomes, such as operative time and warm ischemia time, among three groups consisting of 10 consecutive included patients. These findings strongly suggest that RAPN using hinotori for patients with small renal tumors could facilitate satisfactory outcomes with respect to both safety and disease control. In fact, it seems to be unlikely to occur to disturb the surgical procedures during RAPN using hinotori, and according to our impression, this may be mainly caused by the flexible movements of robotic arms without their collisions. Accordingly, we believe that hinotori could be safely applied to more complex tumors than those included in this series.

Several limitations of this study should be mentioned. First, being prospectively performed, this study consisted of a small number of patients and focused on perioperative outcomes alone; therefore, it will be necessary to assess long-term outcomes of RAPN using hinotori, including prognostic and renal functional outcomes, based on data from a much larger number of patients. Second, it will also be required to comprehensively compare clinical outcomes of RAPN using hinotori with those using other robotic systems, particularly the most common platform, da Vinci, by a reliable method, such as propensity score matching. Finally, this study employed only three well-experienced robotic surgeons who had performed robotic surgery for >250 cases, including RAPN for >50 cases, as operators, before the introduction of hinotori at our institution. Therefore, it remains unclear whether the present results will also be applicable to operators in majority of institutions.

Conclusions

This is the first study to report the perioperative outcomes of RAPN using the newly developed hinotori surgical robot system. In this study, a total of 30 consecutive patients with small renal tumors were prospectively included, and RAPN could be completed as planned in all 30 cases without severe adverse events, resulting in the achievement of trifecta and MIC outcomes in 100% and 96.7% of these patients, respectively. To confirm whether hinotori could facilitate outcomes comparable with existing robotic systems, such as da Vinci, in patients undergoing RAPN, further comparative studies will be necessary.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Abbreviations Used

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