Perioperative outcomes of robotic versus laparoscopic distal gastrectomy for gastric cancer: a meta-analysis of propensity score-matched studies and randomized controlled trials

Gastric cancer (GC) has been identified as one of the most common cancers, the incidence of which is only second to lung cancer in China [1]. Radical gastrectomy with regional lymph node dissection is always the standard procedure for patients with GC [2]. At present, laparoscopic gastrectomy has been become the mainstream surgical method due to its advantages of less invasiveness, less pain, better cosmetic effect, faster recovery, and shorter hospital stays compared with open gastrectomy [3]. Although, 3D-laparoscopy can provide clear stereoscopic imaging effects, the limitations in straight instruments, amplified tremor, and the uncomfortable position of surgeons are still problems should not to be neglected [4]. The appearance of da Vinci robotic surgery system solved these problems well [5]. In recent years, this new type of surgery gradually gained the favor of surgeons, because of its 3D high-definition vision, multi-degree-of-freedom rotatable wrist device, tremor filtration, better ergonomics, and remote surgical consultation [6]. However, several high-quality research should be needed to prove the short-term perioperative outcomes and long-term surgical outcomes of robotic surgery.

From the robotic gastrectomy (RG) first be reported by Hashizume et al. in 2002 [7] up to now, several studies have compared the perioperative outcomes of RG with laparoscopic gastrectomy (LG) for patients diagnosed as GC [7‐10]. Of which, many studies mixed distal gastrectomy, proximal gastrectomy, and total gastrectomy together for comparation [10, 11]. This can lead to very serious confounding bias, and affects the accuracy of almost all the perioperative outcomes, especially in the terms of operative time, blood loss, numbers of retrieved lymph nodes and the incidence of anastomotic leakage. Therefore, we performed a meta-analysis focused on distal gastrectomy for patients diagnosed as GC. Hitherto, only one meta-analysis of non-randomized controlled trials (non-RCT) compared robotic distal gastrectomy (RDG) with laparoscopic distal gastrectomy (LDG) for GC has been reported by Gong et al. in 2022 [12]. However, several studies being included are small sample volume studies and initial results in learning curve of robotic surgery [13‐17], which are the major reason for high heterogeneity of many outcomes. In the hierarchy of research designs, the results of RCTs are considered the highest level of evidence. Propensity score-matched (PSM) analysis remove the confounding factors and overcome possible selection bias in observational studies, improve the quality of evidence approach to the level of RCT [18]. In order to make a high-quality comparison on the safety and feasibility of RDG versus LDG, we performed this meta-analysis only included PSM and RCT studies compared RDG with LDG for patients with GC.

Minimally invasive is one of the important directions of surgery. Laparoscopic radical gastrectomy is currently the most widely used minimally invasive technique for GC. Several studies have proven the excellent surgical and oncological outcomes [34‐36]. In recent years, a new form of surgery, robotic gastrectomy gradually developed. More and more studies have explored the safety and feasibility of robotic gastrectomy for GC [8, 11, 37]. However, their quality of evidence is jagged. Some studies compared the outcomes of RG and LG mixed different types of gastrectomy together [10, 24, 38]. But we all know that the extent of gastrectomy and lymph nodes dissection plays a critical role in the operative time, blood loss, number of retrieved lymph nodes, resection margin and incidence rate of various complications. Some studies reported the outcomes of small sample volume data and initial results in learning curve of robotic surgery [13‐17]. The results of remaining big sample volume studies compared RDG with LDG were yet not entirely consistent. So that there are still controversies on the safety and efficacy of RDG in patients with GC. Therefore, a high-quality meta-analysis is necessary, and we performed it only included PSM and RCT studies focused on distal gastrectomy for the first time. In summary, the present study revealed that RDG has better surgical outcomes, faster postoperative recovery, and similar incidence rate of complications compared with LDG.

The present meta-analysis showed that the operative time was significantly longer in RDG group compared with LDG group. This is also a universal result, because the additional time, nearly half an hour, was required for docking and preparation [39]. The overall mean difference (MD = 31.42, 95% CI [22.88, 39.96]) revealed by the resent meta-analysis in operative time was coincided with the time for docking. Therefore, it would be impartial for RDG to calculate operative time after docking when compared with LDG, but most of studies didn’t do as this. Another important factor that affects the operative time is learning curve. Kim et al. [40] have reported that approximately 25 cases were needed to overcome operative time-learning curve sufficiently to gain proficiency for RG. Huang et al. [41] also reported that both operative time and docking time decreased and stabilized after 25 procedures for RG. The study performed by Li et al. [25] revealed that the operative time in RG was similar to that in LG after overcoming learning curve. Among the included studies in this meta-analysis, only one RCT indicated that all the RDG were performed by surgeons with experience of more than 50 robotic operations for GC before joining the trial [8]. One PSM study indicated that RDG were performed by one surgeon with experience of 14 robotic operations for GC [27]. As to the rest of studies, just a handful of initial results within learning curve were incorporated, and the proportion is very low. But to get more rigorous results, some large sample RCT studies that exclude the results within learning curve are still needed.

The meta-analysis revealed that RDG was associated with less blood loss and more retrieved lymph nodes. Manipulating in the correct anatomical gap and complete mesangial resection play a crucial role in reducing blood loss and ensuing the numbers of retrieved lymph nodes for radical gastrectomy [42]. The da Vinci vision system delivers highly magnified, 3D high-definition views of the surgical area, and it is more conducive to the identification of anatomical structures and gaps. The LDG included in the meta-analysis were performed using 2D laparoscopy with lowly magnified and 2D low-definition views. The visual difference between RDG and LDG should be the main reason for the statistically significant in blood loss and numbers of retrieved lymph nodes. Recently, 3D laparoscopy is widely used in surgical field. There is also study reported that 3D-LDG presented more retrieved lymph nodes and similar amount of blood loss [43]. Furthermore, the high degrees freedom EndoWrist and tremor filtering provided by da Vinci robotic surgery system benefit to the accuracy of operation, the bipolar Maryland forceps have a better hemostatic effect.

For postoperative recovery, our meta-analysis suggested that RDG had an earlier time to first flatus and liquid intake than LDG. However, there was no statistical differences in time to start soft diet and postoperative hospital stays between the two groups. Time to first flatus is an important indicator to reflect the recovery of gastrointestinal function after gastrectomy. Theoretically time to first liquid intake often consistent with time to first flatus. However, it would influence the accuracy of the two outcomes seriously along with the widespread development of enhanced recovery after surgery (ERAS) [44, 45], which was not indicated in the included studies. Habitually some medical institutions like to give patients soft diet or discharge after the risk period of anastomotic leakage, so that these two indicators were sometimes subjected to subjective decisions. But we still believe that RDG can accelerate the recovery of gastrointestinal function in patients with GC. These maybe owing to the reduced para-injury, and less pain, stress, inflammation result from precise manipulation in RDG group. The only RCT included in the meta-analysis also indicated that RDG could improve the postoperative recovery course [8].

When assessing the quality and safety of operations, postoperative complication is an important consideration. Here we counted the overall complications, surgical complications, and systemic complications. However, we did not find any differences between the two groups. We think this maybe result from that surgery in LDG group were performed by surgeons with extensive experience in laparoscopic surgery. The RDG group, on the other hand, contained data within the learning curve. Or the sample volume was not big enough to highlight the advantage of RDG.

Although all the studies included in the meta-analysis are high-quality evidences, 7 PSM studies and 1 RCT study, there are still some limitations in this study. First, only one RCT study compared RDG and LDG was published up to now, and was included in this meta-analysis. Second, the results in RDG group were influenced more or less by outcomes within learning curve. Third, this meta-analysis assessed the short-outcomes and safety of RDG versus LDG, however, the long-term oncological outcomes cannot be ignored in robotic surgery.

In conclusion, RDG showed less blood loss and more retrieved lymph nodes, revealed less time to first flatus and liquid intake after operation. The incidence rate of postoperative complications was comparable between RDG and LDG. But the operative time in RDG was longer than LDG group, which we think was mainly delayed by docking. A much better result might be obtained in RDG group, if performed by surgeons mastered in robotic surgery.