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Robotic gastrectomy: the current state of the art.

Since the first laparoscopic gastrectomy for cancer was reported in 1994, minimally invasive surgery is enjoying its wide acceptance. Numerous procedures of this approach have developed, and many patients have benefited from its effectiveness, which has been recently demonstrated for early gastric cancer. However, since laparoscopic surgery is not exempt from some limitations, the robotic surgery system was introduced as a solution by the late 1990's. Many experienced surgeons have embraced this new emerging method that provides undoubted technical and minimally invasive advantages. To date, several studies have concentrated to this new system, and have compared it with open and laparoscopic approach. Most of them have reported satisfactory results concerning the post-operative short-term outcomes, but almost all believe that the role of robotic gastrectomy is still out of focus, especially because long-term outcomes that can prove robotic oncologic equivalency are lacking, and operative costs and time are higher in comparison to the open and laparoscopic ones. This article is a review about the current status of robotic surgery for the treatment of gastric cancer, especially, focusing on the technical aspects, comparisons to other approaches and future prospects.


Introduction
Minimally invasive approaches for gastric cancer is gaining worldwide increasing acceptance. Laparoscopic surgery, introduced by the 1980's, is widely accepted and currently mainstreamed as a minimally invasive approach for many general surgery procedures, including gastrectomy especially for early gastric cancer (EGC).
Since the first case of a laparoscopic gastrectomy (LG) for cancer was reported in 1994, surgeons with sufficient experience in open gastric surgery adopted this new approach for EGC: it offers not only better early post-operative course but also long-term oncologic outcomes comparable to those achieved with open gastrectomy (OG). (1)(2)(3) However, laparoscopic surgery is not exempt from several disadvantages, such as altered operating view, lack of versatility in surgical instrumentation and an indication to treat advanced gastric cancers still to be defined. In an effort to minimize the limitations of laparoscopy, robotic surgery was introduced by the late 1990's; thought this system provides undoubted technical advantages,(4) its role for gastric cancer is still unclear. (5)(6)(7) Since robotic gastrectomy (RG) has been reported, (4,8) the application of this new approach is increasing in experienced centers but, up to date, a limited number of single case studies and not randomized comparative studies have focused on this new method.
The purpose of this article is to review the current status of robotic surgery for gastric cancer, its technical aspects, its comparisons with open and laparoscopic surgery and to suggest future prospects.

Indications
The indications for RG are the same as those for laparoscopic ones (8)(9)(10): minimally invasive surgery (MIS) is indicated for EGC and it is based on the recommendations of the Japanese gastric cancer treatment guidelines and classification (11,12) as well as the fact that the oncological safety of MIS for advanced gastric cancer remains controversial. According to the articles present in literature up to date, we can summarize as follow: -Indications for RG with limited lymphadenectomy: STAGE IA.
Mucosal and submucosal tumor, if eligible, is first considered for endoscopic resection. In case of failed attempts or not suitable to this approach, it can be a candidate for a RG with limited lymphadenectomy. Specific exclusion criteria or contraindications for robotic surgery, as for laparoscopic surgery, include intolerance to pneumoperitoneum and oncologically contraindicated preoperative findings of T4b cancers or distant metastases.

Operative strategy
Specific characteristics of robotic surgical system and operating room configuration have been previously described in detail. (4,8- The patient-side cart is now moved next to the patient and the robotic arms are connected to the ports (Docking procedure). Surgeon holds the curved bipolar Maryland forceps by the first arm and the ultrasonic shears (or a monopolar device) and the Cadiere forceps by the second and the third arm.
Before proceeding with the main surgical steps, operative field needs to be prepared at least with three manoeuvres: -Gastric decompression with insertion of nasogastric tube or alternatively with a 9 cm long 19 gauge needle introduced percutaneously, in case of gastric distension. (18) -Liver retraction, with one of the various methods described up to date, (19)(20)(21) is a prerequisite for complete exposure of the anterior surface of the hepatogastric ligament.
-Intra-operative tumor localization in order to determine the resection extent during distal subtotal gastrectomy achieved by dye injection, intra-operative endoscopy, (8) or laparoscopic ultrasound, (9,22) or endoclips placement and then abdominal X-ray evaluation. (23) The following are the main surgical steps respectively for robotic subtotal gastrectomy and total gastrectomy.
(2) Total gastrectomy with splenectomy • Full mobilization of the distal pancreas and the spleen.
• Linear or circular staplers including transoral anvil placement.
3. Skill 1) What skills can be improved with robotic technology?
The robotic surgery system facilitates the process of performing laparoscopic surgery and provides: • Three dimensional (3D)-image; • An intuitive translation of the instrument handle to the tip movement, thus eliminating the mirror image effect; • Coaxial alignment of the eyes, hands, and tool tip image; • Motion scaling; • Tremor filtering; • An internal articulated endoscopic wrist, providing an additional three degrees of freedom.
This computer-enhanced surgical system thus allows surgeons to overcome various difficulties during endoscopic surgery. (4,8) 2

) Dissection of splenic vessels
The small branches of the splenic vessels are easily identified and preserved allowing a pancreas-spleen-preserving D2 lymphnode dissection thank to image magnification, tremor filtering, fine circumferential robotic arm movements. This approach allows surgeons to drive the vascular dissection around and to completely clear the lymphatic tissue without any vascular injury with minimal intra-operative bleeding. (13,14) 3

) Isolation of diaphragmatic crura
It's a fundamental step to an en bloc dissection of cardia lymphnodes and is greatly facilitated by wristed instruments that allow complete encircling of the distal oesophagus. (13,15) Moreover, the four-arms robotic surgery system will facilitate the insertion of the anvil head into the oesophageal stump that could be not so easy to do in conventional laparoscopy, (15) and oesophagojejunostomy, which is usually performed in the deep and narrow space of the abdominal cavity, is feasible to execute by the robot-sewing technique. (27) 4) Lymphadenectomy include LN #14v, #8a, #9, #11p, #11d, #12a Relatively difficult areas to access during laparoscopic lymphadenectomy include LN #14v, #8a, #9, and #11. Moreover, the infrapyloric area and the superior mesenteric vein, including stations 6 and 14v, are the most frequent sources of intra-operative bleeding, while the suprapancreatic area including stations 7, 8a, and 9 is the second most frequent source. (13,26) If the dissection along these vessels is easily conducted, the risk of bleeding can be reduced and lymphadenectomy can be better performed. The EndoWrist, tremor filtration, stable operative platform, and three-dimensional vision offered by the robotic surgical system aid the surgeon to perform a more accurate lymph nodes and vessels dissection. (26) Some authors have recently reported a new integrated robotic approach for suprapancreatic D2 nodal dissection which appears to be safe and feasible, even though the number of patients in the study was small.(28) Actually, the role of No. 14v lymphadenectomy in distal gastric cancer is controversial. Dissection of node No. 14v had been a part of D2 gastrectomy defined by the 2nd edition of the Japanese classification, but it has been excluded from the latestedition.(11) However, D2 (+No. 14v) may be beneficial in tumors with apparent metastasis to the No. 6 nodes.

5) Lymphadenectomy in obese and bleeding control
Lymph node dissection around infrapyloric and suprapancreatic area is very difficult to perform in patients with a high body mass index (BMI). Robotic technology may facilitate laparoscopic extended lymphadenectomy in patients who have higher BMI than their Asian counterparts. (16,26) The surgeon can more clearly and definitely identify and easily catch the bleeding vessels using this robotic system than in conventional endoscopic surgery without such a robotic system. This is mainly due to the fact that the robotic system provides a threedimensional view and has few limitations in the movement of the instruments. (8)

Current Status
In recent years, phase III clinical trials provided evidence that LG with lymph node dissection is a safe and effective surgical procedure for the therapy of EGC (6): it produces a better early postoperative course than conventional OG and the long-term outcome of laparoscopy is also similar to that of open surgery. In an effort to minimize the short comings of laparoscopy, especially the technical ones, the robotic surgery system was introduced as a solution.
It is actually considered as a new technology that holds significant promises for the treatment of gastric cancer, although scientific evidence is still lacking.   The largest study is that of Song et al. (9) published in 2009 about their initial 100 cases of robot-assisted gastrectomy with lymph node dissection followed by another one (17)

Comparative studies
Several retrospective comparative studies from Europe and     In terms of intra-operative outcomes, two studies(25,36) find a clinical trend in favour of robotic approach with less blood loss, although the difference is not statistically significant in the first one.
In one study, (35) the estimated blood loss difference observed is of minimal clinical significance. Any articles has demonstrated that the hospital stay of the robotic group was statistically lower than the laparoscopic ones, on the contrary, in one report (36) hospital stay appears to be on average longer for the robotic group, although median days to discharge are similar. Morbidity appears to be lower in robotic group for an author, (25) comparable for other ones. (35)(36)(37) Sound oncologic operative outcomes are especially described by two studies. (36,37) The second one, that is also the most numerous,

Oncological outcomes
Multi-center, randomized, controlled trials are undoubtedly needed to establish the oncological adequacy of RG. The studies performed in Korea are done for EGC only and few trials in Europe have enrolled more advanced gastric cancer stages; the role of robotic surgery in both cases, but especially in the second ones, remains to be delineated, mainly because it is not yet known which is that of laparoscopy.
An interesting aspect that could be investigate in future is in fact regarding the role of minimally invasive approach for the treatment of advanced gastric cancer. Adjuvant chemoradiation and chemotherapy has seemed to increase life expectancy in node-positive gastric cancer patients. In the near future, new approaches to gastric cancer management will provide novel opportunities of treatment, including immunochemotherapy and molecular-targeted therapies.
In this context, minimally invasive surgery could play a key role in improving post-operative course and accelerating times to adjuvant treatments, (15) and especially robotic surgery might be a correct alternative to laparoscopic approach or the first choice for selected cases.

Surgeon's skill
It's ostensible that robotic system can improve surgeon dexterity by performing more precise and safer operative technique in a minimally invasive way due to its technologies, even if it is unproven to date. If it will be demonstrated, this skill could improve experienced laparoscopic surgeon performance, but could especially be a turning point for less accomplished ones. As Jayaraman et al. (39) have reported in their article, robotics may allow less experienced surgeons with fundamental knowledges to perform more complex operations without first developing advanced laparoscopic skills.
Another favourable aspect, is regarding the robotic learning curve. In a report comparing the learning curve between conventional laparoscopy and robotic assistance in surgical tasks, some authors(40) demonstrate that laparoscopic surgery showed a steep learning curve, whereas robot-assisted surgery showed better results from the beginning of the initial case with a shallower learning curve, showing the easy adaptability of robot-assisted surgery.
Further, the growing application of pre-operative simulator technology in surgical robotics may considerably decrease the learning curve of robot-assisted operations (36) and so accelerate the process of robotic adoption in gastric surgery.

Conclusion
This systematic review is to date the more recent. Robotic surgery is actually endowed with very interesting aspects and promising outcomes that could ultimately offer some benefits for the treatment of gastric cancer. Larger numbers of studies and more specific evaluations are needed to prove it and especially to refute pitfalls and disadvantages that are present as well.
On the other hand, as we observed in laparoscopic surgery, to validate the role of robotic surgery will take many more years.