Gastric cancer is one of the most common malignant tumors and its mortality rate is second only to lung cancer. Globally, there are about 934,000 new cases of gastric cancer and about 7,000 deaths per year, of which China and Japan account for about 56%. Although surgery is still the main means of gastric cancer treatment, the overall treatment mode has changed significantly: from general major gastric resection to radical surgery with the purpose of lymph node removal; from anatomy-based surgery to surgery based on anatomy, tumor biology and immunology; from emphasizing only the safety of surgery to the unification of radicality, safety and functionality; from emphasizing only the removal of the tumor to the removal of the primary tumor. from surgery based on anatomy to surgery based on anatomy, tumor biology and immunity; from surgery based on safety to radical, safety and functionality; from surgery based on removal of tumor to surgery based on removal of primary tumor and invaded organs, complete removal of regional lymph nodes and killing of cancer cells shed in abdominal cavity; from single surgery to new treatment model based on perioperative treatment plus standardized surgery. In recent years, the biggest progress of gastric cancer treatment is to significantly improve patients’ survival through the integrated treatment mode of perioperative treatment and adjuvant radiotherapy for gastric cancer. Staging of gastric cancer The reasonable staging of gastric cancer is important for guiding the selection of comprehensive treatment plan and judging the efficacy and prognosis. Since the release of the 1st edition of TNM (Tumor-Node-Metastasis) staging standard in 1977, TNM staging has been one of the main methods to guide the clinical staging of gastric cancer, and it is also the standard staging method adopted by the National comprehensive Cancer Network (NCCN) clinical practice guidelines for gastric cancer later. Since January 1, 2010, the American Joint Committee on Cancer (AJCC) and the International Union for Cancer Control (UICC) have promulgated and implemented the 7th edition of TNM staging criteria for gastric cancer. The new TNM staging criteria for gastric cancer were also released at the same time as an important part of the TNM staging criteria. Compared with the 6th edition promulgated in 2003, the new staging criteria have made significant adjustments to the determination of tumor infiltration and lymph node metastasis, including: 2. Selection of reasonable treatment for early gastric cancer The Japanese Gastrointestinal Endoscopy Association first introduced the concept of early gastric cancer in 1962, with the aim of early detection and improving the 5-year survival rate of gastric cancer after surgery. Early gastric cancer refers to cancerous tissue confined to the gastric mucosal membrane and submucosal layer, regardless of its size and whether it has lymph node metastasis or not. Early stage gastric cancer accounts for about 10% of gastric cancer in China, 30% in Korea and 50%-70% in Japan, which is mainly due to the improvement of early diagnosis and the result of screening of high-risk groups. It is generally believed that lymph node metastasis can also occur in the early stage of gastric cancer, so D2 radical surgery has been used as the standard surgery for early gastric cancer and has achieved very good results both at home and abroad. With the in-depth study of biology and clinicopathology of early gastric cancer, there is a certain understanding of the law of lymph node metastasis and biological behavior of early gastric cancer. Especially, many international centers have reported that the 5-year survival of patients with early gastric cancer is close to 90% after surgery, and the treatment of early gastric cancer has undergone great changes, i.e. surgery to reduce the scope of gastrectomy and lymph node dissection is proposed, including endoscopic mucosal resection (EMR), endoscopic submucosal dissection (EMR), and lymph node dissection (EMR). submucosal dissection (ESD), laparoscopic wedge resection (LWR), laparoscopic intragastric mucosal resection (IGMR), and laparoscopic radical resection of gastric cancer. A large number of long-term follow-up results show that minimally invasive surgery does not increase the recurrence rate of cancer after surgery as long as the surgical indications are properly mastered; moreover, postoperative patients have less pain, faster recovery of gastrointestinal function, smaller abdominal wall scar and less impact on the immune function of the body, and lower complication rate. 2.1 EMR and ESD The currently accepted indications for EMR in the treatment of early gastric cancer are intraparenchymal carcinoma (cTla) visible to the naked eye below 2 cm, with differentiated tissue type and without ulcer formation. It has also been demonstrated that lymph node metastasis is rare in cases meeting these indications. If postoperative pathology confirms that the tumor has infiltrated the superficial subepithelial layer without vascular or lymphovascular invasion, additional gastrectomy or close follow-up can be performed; if the infiltration reaches SM1 with vascular or lymphovascular invasion or the infiltration reaches the deep subepithelial layer SM2, D2 radical surgery for gastric cancer is added. ESD has the following advantages over EMR: (1) the scope and size of resection can be controlled, and even large tumors can be completely resected; (2) ulcerative lesions are not a contraindication to ESD. Therefore, ESD can accomplish complete resection of larger tumors or even ulcerated lesions. The biggest problem facing EMR or ESD is how to avoid underestimating the depth of infiltration and lymph node metastasis of lesions in preoperative diagnosis, and improving the accuracy of preoperative staging will be the key to the development of EMR. 2.2 Laparoscopic-assisted gastrectomy In today’s world where more and more attention is paid to minimally invasive treatment, more and more medical institutions are applying laparoscopic surgery in the treatment of gastric cancer. Japanese scholars suggested that about 20% of patients in gastric cancer surgery are suitable for laparoscopic gastrectomy. However, to date, the discussion on comparing laparoscopic (adjuvant) surgery for gastric cancer with open surgery still lacks large-sample randomized controlled studies, and only a few results from small-sample controlled trials are available. Among these results, there is no high-level evidence suggesting an advantage of laparoscopic surgery as a minimally invasive treatment in terms of indicators such as surgical bleeding, respiratory dysfunction, anesthetic drug use, and hospital days. Thus, to date, laparoscopic surgery has remained only an investigational treatment for patients with stage IA, IB. In addition, the Japanese Society of Laparoscopic Surgery Guidelines published in September 2008 only listed the recommendation for laparoscopic surgery for gastric cancer as “C” (insufficient evidence). Therefore, although it is technically feasible to perform the same D2 lymph node dissection as open surgery for strictly selected gastric cancer patients, there are no published clinical studies with large samples and designs in accordance with the principles of evidence-based medicine, and further exploration of laparoscopic gastric cancer surgery is needed. 2.3 Minimally invasive surgery with preserved function There are three main types of minimally invasive surgery with preserved function as follows: ① laparoscopically assisted vagus nerve preserving radical gastrectomy for gastric cancer; ② pylorus preserving gastrectomy (PPG); ③ laparoscopic vagus nerve preserving partial gastrectomy (laparoscopy (3) laparoscopy assisted vagus sparing segmental gastrectomy (LAVSSG). These procedures mainly preserve the hepatic and abdominal branches of the pyloric vagus nerve, thus effectively reducing the improved postoperative gastrointestinal tract, reducing the incidence of gallstones and diarrhea, and improving the quality of patient survival after surgery [l4], but their application in conventional treatment is not common due to the overlap between their indications and endoscopic surgery. It should be chosen with caution in patients of advanced age and poor systemic status. However, it may also be re-evaluated along with future advances in diagnostic techniques (sentinel lymph nodes, etc.) and changes in standard surgery, as local resection with preservation of function can maintain a better postoperative quality of life. 3.Comprehensive treatment of progressive gastric cancer 3.1 Surgery The long-term survival rate of patients with progressive gastric cancer is less than 30%. Among the comprehensive treatment options for gastric cancer, surgery has always occupied a dominant position. At present, gastric cancer surgery has reached two preliminary consensus: (i) surgery alone cannot achieve biological cure, even if the scope of resection and lymph node dissection is expanded; (ii) for gastric cancer patients without distant metastasis, palliative resection has better effect than those without surgery. The more uniform understanding of progressive gastric cancer is the standard surgery performed mainly for the purpose and standard of radical resection. It requires resection of more than 2/3 of the stomach and D2 lymph node dissection. In contrast, there are also non-standard procedures that vary the extent of resection and lymph node dissection according to the extent of the lesion. 3.1.1 Lymph node dissection scope In 1962, the first edition of the Japanese standard of care for gastric cancer was published, which confirmed that complete lymph node dissection for gastric cancer could significantly improve the 5-year survival rate. After that, the research on the scope of lymph node dissection has been a hot spot in the clinical research of gastric cancer, and there are many controversies among scholars about the scope of lymph node dissection. Most Japanese, Chinese, Korean and some European and American authors advocate extended lymph node dissection (ELND) for gastric cancer, while most European and American investigators have a negative attitude towards it. However, from the latest 2010 edition of the guideline surgical treatment principles, we can see that the biggest change is undoubtedly that Western oncologists have started to fully accept the opinion of Asian scholars, and through further in-depth analysis of the issue of lymph node dissection in gastric cancer, D2 lymph node dissection including lymph nodes around named vessels of the abdominal trunk branches has become the standard treatment. According to a retrospective analysis of 1,377 resected gastric cancer cases in the US Epidemiology and End Results (SEER) database, patients with 15 or more N2 lymph nodes or 20 or more N3 lymph nodes detected had the longest survival for patients with progressive gastric cancer. However, the Japanese JCOG9501 trial confirmed that D2+PAN D clearance should not be routinely used for curable gastric cancer through a randomized controlled study of D2 lymph node dissection versus D2+ para-aortic lymph node dissection (PAN D). An in-depth analysis of the classical literature also revealed a trend toward higher survival rates after D2, with biased results due to high perioperative mortality resulting from combined splenectomy or pancreatectomy. The results of D2 lymph node dissection with preservation of the pancreas reported by the Italian Gastric Cancer Study Group confirmed that perioperative complications and mortality rates for D2 surgery were similar to those for D1 surgery. Subgroup analysis of the controversial INT0116 study by Enzinger et al. also found a trend toward improved survival with either D1 or D2 surgery in centers with a high number of patients with gastric cancer. In contrast to the previous NCCN version, this edition of the guideline specifically states that “‘modified’ D2 surgery (without combined pancreatectomy or splenectomy) performed by experienced surgeons in larger oncology centers does result in lower mortality and survival benefits”. Therefore, “radical surgery for gastric cancer should be performed by experienced surgeons in a large oncology center and should include regional lymph node by perigastric lymph node dissection (D1), as well as lymph nodes accompanying named vessels of the abdominal trunk (D2), with the aim of examining at least 15 or more lymph nodes”. 3.1.2 Extended radical surgery for gastric cancer refers to primary cancer or metastases directly invading the perigastric organs (T4) or lymph node metastases up to N2, which can still be resected radically; the scope of resection includes (i) extended combined resection combined with resection of other organs; (ii) lymph node dissection at the level of D2 or above, such as No.16 group lymph nodes, etc., when the disease stage is IIIa, IIIb and part of stage IV. Surgery. (1) Expanded combined resection with combined resection of pancreas and spleen Since group 10 and 11 lymph nodes must be removed when D2 removal of upper gastric cancer is performed, some scholars have suggested that combined left hemipancreatic, splenic artery and vein and splenectomy should be performed, but the incidence of serious complications such as pancreatic repeated, abdominal infection and diabetes mellitus is higher after this operation.Wang JY et al. reported that 84 patients with progressive gastric cancer were randomly divided into pancreatic-preserving radical gastric cancer group (38 patients) and combined pancreatic body and tail resection group (46 patients), and the complication rates of the two groups were 23.7% and 52.2%, respectively; the postoperative 5-year survival rates were the opposite, 42.4% and 35.6%, respectively, suggesting that combined pancreatic body and tail resection should not be routinely performed for progressive cancers in the middle and upper regions of the stomach. Therefore, in cases where the cancer does not infiltrate the pancreas and only metastasis to the splenic hilum or parapleural lymph nodes is suspected, combined pancreatectomy is usually not advocated, and the indications for left hemipancreatic resection combined with splenectomy are limited to cases where the gastric cancer directly invades the pancreas. For upper progressive gastric cancer, there has been a debate on whether combined splenectomy should be performed for complete clearance of lymph nodes in groups No.10 and 11d. In particular, western scholars regard combined splenectomy for gastric cancer as a high-risk surgical procedure. Recent studies have found that most of the metastases in the splenic hilar lymph nodes are in the fundic gonadal region, with an incidence of 9.8%-14%, and mainly occur in advanced tumors that have infiltrated into the plasma membrane (T3) or outside the plasma membrane (T4). It is rare for gastric cancer to infiltrate directly into the spleen, and the efficacy of prophylactic splenectomy is not better than that of splenoprotection, so it is not recommended to perform this procedure routinely. It is currently being explored in several clinical studies, including the JCOGO110 trial in Japan. However, at least, the current preliminary consensus is that stage IIIb and IV carcinomas in the gonadal region of the fundus or the large curved side of the gastric body region with direct tumor infiltration of the spleen or bloodstream metastases to the spleen and metastases to the splenic portal lymph nodes should be performed by splenectomy. In conclusion, if the cancer in the middle or upper part of the stomach invades the body and tail of the pancreas, whole stomach combined with splenectomy and pancreatic body and tail should be performed; if there is metastasis in the lymph nodes of group 10 and 11, combined splenectomy can be considered; if there is no metastasis in the lymph nodes of group 10 and 11, prophylactic splenectomy should not be performed. (2) The significance of expanded lymph node dissection at the D2 level or higher is unclear. The significance of prophylactic No.16 group lymph node dissection has been denied by the results of the Japanese randomized controlled trial (RCT) CJCOG9501). In patients with No.16 group metastases without the presence of other nonradical factors, D2+No.16 group clearance has a poor prognosis despite the possibility of achieving RO resection. Whether to perform D2 clearance or D2+No.16 group clearance after reaching downstage with preoperative chemotherapy is still under clinical investigation. In conclusion, the new treatment model of “surgery + perioperative treatment” has entered the stage of gastric cancer treatment. With the development of medical technology, new techniques are gradually applied in clinical practice. Only by actively using evidence-based medicine and combining the strengths of various treatment methods for comprehensive treatment of gastric cancer cases can we ultimately achieve the goal of improving patients’ prognosis and life quality.