Gastric Carcinoma
Gastric carcinoma is among the most common solid malignancies worldwide, with an incidence of over 1 million new cases [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 being gender-dependent at 30% for men and 33% for women [2]. While in Asia, due to screening programs, 5-year survival rates of over 70% are achieved, gastric carcinoma in this country 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 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. 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.
Early gastric carcinomas with at most one "expanded criterion" can also be resected curatively endoscopically [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 expanded criterion is present, 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.
For early gastric carcinoma, the indication for surgery exists whenever the carcinoma confined to the mucosa (T1a) cannot be curatively resected endoscopically or when greater depth of invasion (T1b) increases the risk of lymph node metastases and adequate lymphadenectomy is essential for 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, shortened postoperative atony, faster mobilization, and a shorter hospital stay [5, 9-11, 16-18]. Overall morbidity after laparoscopic surgery is significantly lower in RCTs: laparoscopic vs. open 2.0–2.8% vs. 2.0–57.1% [13, 18]. The 30-day mortality of laparoscopic and open techniques is the same 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].
Sufficient data are available to make reliable statements about the oncological outcome after laparoscopic resection of early gastric carcinomas. The Korean COACT0301 trial found a 5-year DFS (disease-free survival) of 98.8% in the laparoscopic group and 97.6% in the conventionally open group. The 5-year overall survival was almost 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 (cardiac 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 rapid section examination should take place. 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-grade 1 studies (RCT) for oncological equivalence are still pending.
The current German S3 guideline (update 2019) does not generally recommend laparoscopic procedures for curative surgery of gastric carcinoma [3]. The goal of cure should be pursued in all functionally operable patients with T1 to T4 tumors [43]. Patients with T4b tumors involving unresectable structures and those with distant metastases should not undergo radical surgery.
Role 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 study (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 minimally invasive gastrectomies (MIG) is based on smaller studies that investigate the postoperative outcome as the primary endpoint. Notable are the LOGICA study (NCT02248519) and the STOMACH study (NCT02130726), which compare postoperative morbidity, length of stay, and surgical quality of laparoscopic gastrectomy to 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. A subgroup analysis showed less blood loss in the D2 lymphadenectomy in the robotic group [47, 48].
A Japanese prospective multicenter single-arm study for gastric carcinomas in UICC stage I/II showed lower morbidity after robot-assisted gastrectomy compared to a historical laparoscopic cohort [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 always show equivalent lymph node numbers even for selected, technically demanding lymph node stations [50, 51].