Robotic vs. laparoscopic liver surgery: what are the advantages of the robot?

Introduciton

Minimally invasive liver surgery (MILS) ads less morbidity and mortality to the patients compared to open procedures. The first laparoscopic liver resections (LLRs) were performed in the 1990s. After an initiation phase especially, the removal of smaller tumors (<5 cm) on good reachable liver segments (II–VI) was recommended (1). Later all liver segments were considered for laparoscopic resections (2). After expert meetings and consensus conferences (2008, 2014, 2016) no limitations for selected malignant liver tumors such as hepatocellular carcinomas (HCC) or colorectal liver metastases (CLM) were identified for the use of laparoscopic liver surgery (3). The oncological outcome of MILS is similar to open procedure (4-7). Today, it is clear that major liver resections, associating liver partition and portal vein ligation for staged hepatectomy (ALLPS) and living donor liver resections can be performed minimally invasive (2,8,9). Behind these facts MILS has been recommended as standard of care for selected liver resections such as left lateral segment removals (10). The problem is that there is a quiet high learning curve for MILS (11). Surgeons need to be trained in hepatobiliary and minimally invasive surgery. This needs dedicated people and high-volume centers which can offer the volume load for the learning curves.

The robotic platform offers some innovations which may facilitate MILS (12). Several maneuvers might be easier compared to standard laparoscopy which could reduce the learning curve. Especially the Endowrist, which gives more degrees of freedom at the tip of the instruments, is a new helpful tool. Hereby the instrument’s tip can be handled like the surgeon’s prolonged hand in the patient’s body. Sewing and vessel dissection becomes easier and more precise. The control of three instruments and the camera by the console surgeon offers excellent control of the operation situs. This is helpful especially in case of emergency situations like unexpected bleeding. Moreover, the robot makes minimally invasive surgery less exhausting compared to conventional laparoscopy. The surgeon can sit in a relaxed manner at the console and needs not like sometimes in conventional laparoscopy strength killing positions. Nevertheless, the robot has its limitations. The missing haptic is the most important limitation. In conventional laparoscopy this can sometimes be compensated by palpating structures with the instrument. The surgeon gets feedback via the tool through the hand which gives him an idea of the consistence. In robotics this is not possible. The so called visual haptic which means the behavior of the structure by palpating it with the robotic tool gives you an idea of its consistence based on your experience, is currently the way to compensate the missing haptic feedback. Furthermore, the current robots are no really robots. They are tele-manipulators. All movements of the instruments are driven by a surgeon from a console. Nevertheless, the implementation of robots in minimally invasive surgery is rising worldwide and the trend continues. For liver surgery, the robot has been considered as safe and effective tool (13).

Regarding the endpoints of outcome in perioperative data or oncological outcome there are not many studies, which demonstrated a clear superiority of the robot vs. conventional laparoscopy. Especially in MILS there are no randomized trials comparing these issues. Based on the literature experiences on a decade (2010–2020) comparing laparoscopic with robotic liver surgery we summarize the results of the current literature and add our own experience.

Methods

Literature research

A PubMed research was performed on February 15^th 2021 restricted to articles in English language. The following terms were searched in title, abstract, keywords: robotics, robot, laparoscopic, laparoscopy, and liver surgery. Only articles were selected for the study, which compared laparoscopic with robotic-assisted liver resections (RLRs) based on original data. Meta-analysis and reviews were excluded from the study. Perioperative and if tangible data regarding cost analysis or oncological outcome were summarized and compared between LLR and RLR.

Patient selection

Patients which underwent minimally invasive left lateral liver resection between 2015 and 2020 were selected from the Magdeburg registry of minimally invasive liver surgery (MD-MILS). The data were collected prospectively and analyzed in a retrospective procedure. Only patients with solid tumors were included in the study. Patients with cystic lesions, liver resection for trauma or ablation without liver resection were excluded. Perioperative parameters were selected and compared between laparoscopic versus robotic performed liver resections. Overall and liver surgery related morbidity were quantified. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the ethical board University Hospital Magdeburg (R03-21) and the individual consent for this retrospective analysis was waived.

MILS

LLR was performed in a complete laparoscopic technique. No cases of hand-assisted laparoscopy or hybrid techniques were included. The trocar placement and the technical details of MILS were described elsewhere (14). For parenchymal dissection, we used a harmonic scalpel or the laparoscopic CUSA (cavitron ultrasonic surgical aspirator) or an aquajet. In case if there was no scar from previous surgery, the specimens were placed in a retrieval bag and removed via a Pfannenstiel incision. For RLR, the DaVinci System (Intuitive, Santa Clara, USA) was used. Our techniques of RLR have been described elsewhere in detail (14-19).

Statistical analysis

We analyzed patient characteristics, perioperative parameters and type of procedures between the two groups (LLR vs. RLR). Data analysis was performed using IBM SPSS Statistics for Windows, version 26 (IBM Corp., Armonk, NY, USA). Cross tables and chi-squared test were used for the descriptive analysis and significance test for dichotomous variables. We used number of cases and percentage for data presentation here. The independent samples t-test was applied for the continuous variables.

Results

Review of the literature

Between 2010 and 2020, 29 papers were selected regarding the inclusion criteria. In one study the analyses were divided in substudies regarding major or minor liver resections (20). Taking this into account, nine studies included only patients with minor and five studies with major liver resections (14,20-31). Fifteen studies enrolled patients with major and minor liver resections (32-46). These studies included 1,392 patients which underwent robotic and 1,965 patients which underwent conventional LLR. The mean age of patients in RLR was 50.4–66.6 years while it was 47.0–66.7 year in LLR. The mean body mass index (BMI) in the RLR was 24.0–31.0 kg/m²vs. 23.5–29.5 kg/m² in the LLR procedures. The mean tumor size in the RLR cases was 3.2–7.1 cm while it was 2.36–7.0 cm in the LLR patients (Table 1).

The mean operative time was between 121–425 min in the RLR and 130–565 min in the LLR cases. The conversion rates were around 0–20.0% in the RLR and 0–30.9% in the LLR studies. Mean estimated blood loss was 30–500 mL in the RRL vs. 30–513 mL in the LLR patients. Blood transfusion was needed in 0–25.0% of patients which underwent RLR and 0–23.1% of patients which were operated by conventional laparoscopy. Perioperative overall morbidity was reported in 0–68.0% in RLR cases and 0–35.3% of LLR procedures. The mortality was 0–10.0% in the RLR and 0–5.0% in the LLR cases. Margins with residual tumor (R1) in case of malignancy were present in 0–11.1% of RLR cases and 0–23.1% in LLR procedures (Table 2).

Minor and major minimally invasive liver resections

The nine studies including only minor MILS included 157 patients which underwent RLR and 356 patients which underwent LLR (14,20,21,23,24,26-28,30). The mean BMI of theses RLR cases was 26.1–31.0 kg/m² and 23.2–29.0 kg/m² in the LLR patients. The mean tumor size was between 2.67–5.59 cm in the RLR and 2.36–4.95 cm in the LLR groups. The mean operation time in the RLR studies including only minor cases was 121–321 min and 148–295 min in the compared LLR cases. The conversation rate in the RLR groups was 0–14.3% and 0–9.7% in the LLR patients. The mean estimated blood loss in minor cases was 30–415 mL in the RLR and 30–437 mL in the LLR cases. The transfusion rate varied between 0–14.2% in the RLR and 0–4.7% in the LLR groups. The morbidity and mortality in minor cases was 0–25.0% and 0–2.8% in the RLR vs. 4.7–19.5% and 0–3.6% in the LLR groups. The R1 resection rate was 0–11.1% in the RLR and 0–12.5% in the LLR minor cases (Tables 1,2).

Five studies compared only major liver resections (20,22,25,29,31). These studies included 196 patients which underwent RLR and 222 patients which received LLR. The mean BMI of theses RLR cases was 24.0–28.6 kg/m² and 23.7–29.5 kg/m² in the LLR patients. The mean tumor size was between 4.51–7.10 cm in the RLR group and 4.48–7.00 cm in the LLR group. The mean operation time in the major liver resection studies was 194–456 min in the RLR group and 195–565 min in LLR group. The conversation rate in the RLR cases was 4.0–14.3% and 4.0–25.0% in the LLR patients. The mean estimated blood loss in major cases was 243–625 mL in the RLR and 250–513 mL in the LLR cases. The transfusion rate varied between 25.0–44.0% in the RLR group and 7.7–16.0% in the LLR group. The morbidity and mortality in major cases was 0–28.1% and 0% in the RLR group vs. 10.4–36.0% and 0–4.0% in the LLR group. The R1 resection rate was 0–8.3% in the RLR and 7.4–25.0% in the LLR major case series (Tables 1,2).

Cost analysis

In five papers the costs regarding RLR or LLR were analyzed (20,24,27,34,36). Cortolillo et al. calculated $24,983±$18,329 for the robotic procedures and $30,194±$26,977 for the laparoscopic operations regarding the initial admission. In case of readmission costs for RLR were $18,211±$33,267 and $14,927±$16,818 for LLR. Ji et al. analyzed hospital costs of $12,046 for robotics and $7,618 for laparoscopy. Kim et al. reported of about $8,183 costs for RLR and $5,190 LLR. Mejia et al. calculated mean total charges for minor cases of $39,054.9 [standard deviation (SD) 14,858.3] for full laparoscopy and $50,395.4 (SD 18,224.1) for robotic procedures. For major liver resections in cases of laparoscopy $54,850.3 (SD 13,746.6) and in case of robotics $61,333.2 (SD 19,682.2) were estimated. Packiam et al. calculated full surgical supply costs of $6,553 for robotics vs. $4,408 for laparoscopy (P=0.021).

Oncological outcome

In three papers data about oncological outcome were reported (21,24,41). Berber et al. reported during an observation period of 14 months in patients with HCC and CLM of an equivalent outcome in terms of disease-free survival (DFS) and overall survival (OAS) between robotic and laparoscopic cases. Kim et al. included HCC and CLM cases as malignant tumors in their study. They found no significant differences in DFS and OAS between RLR vs. LLR. The 2- and 5-year DFS were 63.2% and 36.5%, the median DFS was 56 months in both groups. The 2- and 5-year OAS were 96.8% and 91.4% in the RLR and LLR groups. Rahimli et al. included CLM in their study only. They described 1-, 3- and 5-year OAS rates of 84.0%, 56.9%, and 48.7% and 1- and 3-year recurrence-free survival rates of 49.6% and 36.2%, without significant differences between RLR and LLR.

Left lateral liver resections MD-MILS

Twenty-two patients were identified in the MD-MILS regarding the selection criteria. Of these 13 patients underwent RLR and 9 LLR (Table 3). The mean age of the patients was 63.8 years of age, the mean BMI was 28.5 kg/m² (range, 22.0–44.8 kg/m²). In 15 cases malignant [HCC: n=8, CLM: n=4, cholangiocarcinoma (CCC): n=2, melanoma metastasis: n=1] and in 7 patients benign disease (FNH: n=3, haemangioma: n=3, adenoma: n=1) was identified. The mean tumor size of the liver lesions was 5.8 (SD 3.6) cm. Abdominal adhesions as a result of prior abdominal surgery were present in 45.5% of all cases. Mean operation time was 243.2 (SD 80.2) min in the RLR group vs. 160.1 (SD 39.8) min in the LLR group (P=0.01). All other perioperative parameters showed no statistically significant differences between RLR vs. LLR (Table 3). The overall morbidity was 15.4% in the RLR and 22.2% in the LLR, while there was no postoperative liver surgery related morbidity in both groups. No patient died during the hospitalization period.

Discussion

The robot is the next step of evolution in MILS which offers technical innovations that might overcome some laparoscopic limitations. But these technical limitations depend on the experiences and skills of the laparoscopic surgeon and cannot be summarized as general rule for everybody. Various fantastic solutions for technical challenges have been developed by creative surgeons throughout the years. Nevertheless, the Endowrist at the tip of the instruments at the robotic platforms is a clear step forward which provides an enormous benefit in terms of sewing and vessel dissection. This new feature generates an enhanced mobility of minimally invasive instruments, which helps to work very precisely in narrow spaces. This facilitates in MILS the mobilization of the liver from the vena cava, vessel dissection at the hepatoduodenal ligament and control of the hepatic veins (15,16). The surgeon handles three instruments from the console including the camera. Usually, an assistant at the table supports the operation with a further laparoscopic instrument. So, taken together there are four instruments in the abdomen to handle the situs. This generates a very stable operation field which enables fast and controlled maneuvers especially in emergency cases such as unexpected bleeding. Behind these facts the robot may provide benefits especially in advanced cases of MILS. During our review we figured out that in major liver resections in bigger tumors the conversion rate and the R1 resection rate was reduced and in RLR vs. LLR. Even the of morbidity and mortality rates for major cases was reduced in RLR compared to LLR. Although we selected only left lateral liver resections from the MD-MILS, we observed a similar trend in these patients but without statistical significance. Summarizing the findings throughout the reviewed literature, benefits added by the robot in major and more challenging liver resections becomes visible. This hypothesis is supported by a recent review which confirms our findings (47).

Nevertheless, surgery with the robot is more time consuming compared to LLR. Even in the MD-MILS patients the operating time was significantly increased in the RLR vs. LLR. In all studies which calculated costs for the procedures, the robot seemed to be a factor to increase this parameter (20,24,27,34,36). Depending on the region where the study was performed and the factors which were included into the calculation the results vary extremely. But it became obvious during our review that robotic is an independent cost enhancer. In a previous analysis we described that the main proportion of costs for the robot occur during surgery itself, driven by the high material and maintenance costs for the robot. This can partially be compensated by reduced hospitalization of the patients during MILS compared to open surgery. But this benefit becomes irrelevant when RLR is compared to LLR, because there is no difference in hospitalization. Regarding oncological outcome in malignant disease there are only limited results throughout the studies (21,24,41). That MILS has no disadvantage for the patients regarding OAS, DFS and median survival compared to open surgery has already been proven. In our review no significant differences between RLR and LLR could be identified.

The limitations of the current robotic approach may result from the fact that these new tools are currently not really used as robots. The instruments are driven from a console by a surgeon. That makes the robots to a kind of tele-manipulator. No autonomous actions are driven by the machine itself. So, the current technology can be interpreted as an intermediate step to real robotic. Image driven navigation and artificial intelligence are needed to foster an automated system for surgery. This could make surgery faster, more precise and safer for the patients. It depends on the surgeons if they are willing to implement this into routine or if this will be blocked by ethical or legal considerations.

In summary the current robotic systems offer technical innovations which lifts minimally invasive surgery to another level. Dramatic differences at the endpoints of the minimally invasive procedures comparing RLR vs. LLR cannot be evaluated. Maybe in advanced cases the robot has some benefits. The small differences between the procedures regarding their study endpoints are not surprising because at the end the operation stays a minimally invasive procedure no matter if it was performed with the robot or conventional laparoscopy. This brings up the question if we measure the right parameters to compare the procedures. Maybe we should focus less at endpoints and concentrate on intraoperative measures to evaluate the benefits for the operating surgeon who really feels a difference in comfort between robotic and conventional laparoscopy. Nevertheless, the robot provides a technical platform which has the potential to drive surgery in partial or complete automatization which could be of benefits for the patients. It remains the surgeons’ decision if this will be pushed and can be happen in the near future.

Acknowledgments

The authors thank the Faculty of Medicine, University of Magdeburg for supporting the study.

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Digestive Medicine Research for the special series “Hepatic, pancreatic and biliary surgery”. The article has undergone external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/dmr-21-26). The series “Hepatic, pancreatic and biliary surgery” was commissioned by the editorial office without any funding or sponsorship. AAG served as the unpaid Guest Editor of the series and serves as the unpaid editorial board member of Digestive Medicine Research from Aug 2020 to Jul 2022. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the ethical board University Hospital Magdeburg (R03-21) and the individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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