Gastric carcinoma, with a worldwide incidence of over 1 million new cases, is among the most common solid malignancies [1]. In Germany, the incidence is approximately 15,000 new cases per year (about 9,000 men and 6,000 women), with the current 5-year survival rate depending on gender between 30% (men) and 33% (women) [2]. While in Asia, due to screening programs, 5-year survival rates of over 70% are achieved, gastric carcinoma in this region often presents at an advanced stage at initial diagnosis, which can no longer be removed locally by endoscopic resection.
The only option for curative therapy in locally advanced gastric carcinomas and adenocarcinomas of the esophagogastric junction (AEG) currently is oncological-surgical resection with the goal of complete removal of the primary tumor (tumor-free resection margins, R0) and the regional lymphatic drainage pathways (systematic D2 lymphadenectomy) [3].
Endoscopic Submucosal Dissection (ESD)
An exception is made for early carcinomas (pT1a and N0), which can be resected en bloc endoscopically if they meet all of the following four criteria [3]:
- < 2 cm in diameter
- not ulcerated
- mucosal carcinoma
- intestinal type or histological differentiation grade good or moderate [G1/G2)
Since some criteria (grading, submucosal invasion) are only available after precise histopathological diagnosis, endoscopic resection can initially be performed for diagnostic purposes. However, it should be ensured that this is done with the aim of an en bloc R0 resection. Here, endoscopic submucosal dissection (ESD) is the method of choice, as it is the only one that allows a safe en bloc R0 resection regardless of size.
Gastric early carcinomas with a maximum of one "extended criterion" can also be resected endoscopically in a curative manner [3]:
- differentiated mucosal carcinoma (G1/G2) without ulceration and size > 2 cm
- differentiated mucosal carcinoma with ulceration and size ≤ 3 cm
- well-differentiated carcinomas with submucosal invasion < 500 µm and size < 3 cm
- undifferentiated mucosal carcinoma < 2 cm in diameter (provided no biopsy evidence of tumor cells within ≤ 1 cm distance)
If more than one extended criterion is present, an oncological-surgical resection should be performed [3].
Oncological-Surgical Resection
In addition to total and transhiatal extended gastrectomy, depending on the indication and tumor size, partial gastric resection in the form of proximal or distal gastric resection is possible.
In the case of gastric early carcinoma, the indication for surgery exists whenever the carcinoma confined to the mucosa (T1a) cannot be resected curatively endoscopically or when greater depth of invasion (T1b) increases the risk of lymph node metastases and adequate lymphadenectomy is indispensable for safely achieving a cure [3, 4].
For early carcinomas, there is high evidence that laparoscopic procedures are technically safe and oncologically comparable to open surgery, regardless of tumor location and type of resection [5-18]. Compared to conventionally open-operated patients, patients recover faster after laparoscopic resection, show significantly earlier oral tolerance of food intake, reduced postoperative atony, faster mobilization, and a shorter hospital stay [5, 9-11, 16-18]. Overall morbidity after laparoscopic surgery is significantly lower in RTCs: laparoscopic vs. open 2.0-2.8% vs. 2.0-57.1% [13,18]. The 30-day mortality of the laparoscopic and open technique is equal at 0.1-3.0% [4, 5, 19]. An LAD with more than 25 removed lymph nodes and a D2-LAD can be performed laparoscopically without increasing morbidity [17].
There is sufficient data available to make reliable statements about the oncological outcome after laparoscopic resection of gastric early carcinomas. In the Korean COACT0301 trial, a 5-year DFS (disease-free survival) of 98.8% was found in the laparoscopic group and 97.6% in the conventionally open group. The 5-year overall survival was nearly identical at 97.6% in the laparoscopic group and 96.3% in the open group [20]. Other comparative studies came to similar results [11, 21].
For locally advanced gastric carcinomas that are proximally located, gastrectomy is usually required. For adenocarcinomas of the esophagogastric junction (cardia carcinoma, AEG Type II and III), distal esophageal resection is additionally indicated. Depending on the luminal tumor spread, subtotal esophagectomy with proximal gastric resection or esophagogastrectomy may be necessary to achieve an R0 resection. For distal tumors, the proximal stomach can be preserved without worsening the prognosis. An adequate resection margin of 5 cm (intestinal type according to Lauren) or 8 cm (diffuse type according to Lauren) should be aimed for. If the safety margin is undershot orally, a frozen section examination should be performed. Structures adherent to the tumor (e.g., diaphragm, spleen) should be removed en bloc with the tumor if possible. Routine splenectomy should be avoided [22-27].
Numerous studies are now available for laparoscopic procedures for curative surgery of gastric carcinoma, which have a high level of evidence for distal, locally advanced carcinomas and distal or subtotal gastric resections, combining technical feasibility and oncological outcome with the advantages of better early postoperative recovery [19, 28-42]. For proximally located advanced carcinomas, the safety of laparoscopic techniques is proven, but evidence level-1 studies (RCT) for oncological equivalence are still pending.
The current German S3 guideline (update 2019) currently recommends laparoscopic procedures for curative surgery of gastric carcinoma "not generally" [3]. The goal of cure should be pursued in all functionally operable patients with T1-T4 tumors [43]. Patients with T4b tumors involving unresectable structures and those with distant metastases should not undergo radical surgery.
Significance of Minimally Invasive Techniques
Regarding the indication for minimally invasive procedures in advanced gastric carcinoma, the latest results of large prospective randomized studies indicate an equivalent oncological outcome of laparoscopic gastrectomy compared to open gastric resection. A corresponding Chinese study has already shown comparable disease-specific 3-year results [44]. The Korean KLASS-02 (Korean Laparoendoscopic Gastrointestinal Study Group) showed lower postoperative morbidity after laparoscopic gastrectomy with D2 lymphadenectomy, while an equivalent Japanese study demonstrated equivalence [45, 46]. Western evidence on MIG consists of smaller studies that examine the postoperative outcome as the primary endpoint. Notable here are the LOGICA study (NCT02248519) and the STOMACH study (NCT02130726), which compare postoperative morbidity, length of stay, and surgical quality of laparoscopic gastrectomy with open gastrectomy.
Robotics in Gastric Surgery
With the same indication, a Korean prospective multicenter non-randomized study showed equivalent postoperative outcomes in robotic gastrectomy compared to laparoscopic gastrectomy. In a subgroup analysis, there was less blood loss with D2 lymphadenectomy in the robotics group [47, 48].
A Japanese prospective multicenter single-arm study for gastric carcinomas in UICC stage I/II showed lower morbidity after robotically assisted gastrectomy compared to a historical laparoscopic group [49].
The number of resected lymph nodes was not different in this and other studies, so equivalent long-term results are expected.
In larger retrospective series, it has been shown that long-term results after robotic resection are not inferior to those after laparoscopic resection. Already published results on gastric resection could consistently show equivalent lymph node numbers even for selected, technically challenging lymph node locations [50, 51].