The purpose of gastric cancer staging is to measure the early stage of the disease, judge its prognosis, and decide the treatment plan. Under a uniform staging standard, the clinical data can be comparable, and it is convenient for clinicians to summarize and exchange treatment results with each other and to conduct collaborative research on gastric cancer. A simple, accurate and operational staging system is important for the treatment and prognosis of gastric cancer. Over the past half century, several staging methods for gastric cancer have been proposed worldwide, but none of them has been accepted due to the inherent defects of each. Internationally, there are three authoritative institutions on the staging of gastric cancer, namely, the International Union Against Cancer (UICC), the American Cancer Consortium (AJCC) and the Japanese Cancer Society (JCC). There are two major staging systems for gastric cancer, namely, the TNM staging system developed by the International Union Against Cancer (UICC) and the staging system developed by the Japanese Gastric Cancer Research Society in the “Gastric Cancer Statute (GRGCS)” (1). The following is a review of the TNM staging system: Xiong Shaowei, Department of Gastrointestinal Surgery, Peking University Shenzhen Hospital
I. International TNM staging method (UICC 6th edition, 2002) (2)
In 1966, the UICC first formulated the international TNM staging method for gastric cancer, and it has been forty years since then, during which several revisions have been made. The 5th edition of the TNM staging method formulated by the UICC in 1997 is obviously different from the previous staging method in terms of the criteria for lymph node grading, and its main feature is that the number of regional lymph node metastases in gastric cancer is taken as the criterion for lymph node grading, instead of the location of lymph nodes. Based on the 5th edition, UICC developed the 6th edition of TNM staging method in 2002, as follows.
T: primary tumor; TX: primary tumor cannot be evaluated (including incomplete information, no records, etc.); T0: no evidence of primary tumor: Tis: carcinoma in situ, intraepithelial carcinoma not infiltrating the lamina propria; T1: tumor infiltrating the lamina propria or submucosa; T2: tumor infiltrating the muscularis or subplasma layer; T2a: tumor invading the muscularis; T2b: tumor invading the subplasma layer; T3: tumor penetrating the plasma layer, not invading adjacent structures, T3: tumor penetrating the plasma layer When the tumor may have penetrated into the muscular layer and invaded into the gastrocolic ligament, hepatogastric ligament or greater and lesser omentum, but did not penetrate into the visceral peritoneum of these tissues, it is still classified as T2, and if the tumor penetrated into the visceral peritoneum covered by these organs, it is T3; T4: the tumor directly invaded into the adjacent structures. The adjacent structures of the stomach include: spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal glands, kidney, small intestine and retroperitoneum. Tumor extension from the gastric wall to the duodenum or esophagus is determined by the depth of the most severe infiltration including the stomach T.
N: localized regional lymph nodes. NX: regional lymph nodes could not be evaluated; N0: no regional lymph node metastasis; regardless of the total number of lymph nodes resected and examined, if all lymph nodes are metastasis-free, locate PN0; N1: with 1 to 6 regional lymph node metastasis; N2: with 7 to 15 regional lymph node metastasis; N3: greater than 15 regional lymph node metastasis.
M: distant metastasis. MX: distant metastasis could not be assessed; M0: no distant metastasis was found; M1: distant metastasis was present (including lymph node involvement in the hepatoduodenal ligament, posterior pancreas, mesenteric root and parietal abdominal aorta).
Table 1 TNM staging of gastric cancer
Staging T N
T
N
M
Stage 0
Tis
N0 M0
M0
IA period
T1
N0 M0
M0
IB period
T1
N1
M0
T2a/b
N0
M0
Phase II
T1
N2
M0
T2a/b
N1
M0
T3
N0
M0
Phase IIIA
T2a/b
N2
M0
T3
N1
M0
T4
N0
M0
Phase IIIB
T3
N2
M0
Phase IV
T4
N1-3
M0
T1-3
N3
M0
Any T
Any N
M1
Advantages: Since the promulgation of the new staging standard, data from Japanese Katai (3), German Roder (4), Korean Yoo (5) and our own Wang Zhenning (6) have retrospectively analyzed the data of gastric cancer patients and compared the new TNM staging with the original TNM staging (4th edition, 1987), and found that the consistency of each sub-stage and prognosis in the new TNM staging is better than that of the old staging (4th edition), which is a more reasonable indicator to judge the prognosis of gastric cancer. It is a more reasonable indicator for judging the prognosis of gastric cancer, and is simpler, more objective, more reproducible, and easier to be applied.
Disadvantages: (1) In surgery, if more lymph nodes are removed, the number of positive lymph nodes is bound to increase, so the surgeon’s technique of lymph node dissection and the scope of lymph node dissection can affect the staging results. (2) The number of pathological sections per lymph node is not specified, so if a single section of a lymph node is made, there is a greater possibility of missing the diagnosis, leading to wrong staging. (3) Katai in Japan reported that there was no difference in 5-year survival rate between stage IIIB and IV patients in the new version of the TNM staging system (3).
II. Japanese GRGCS staging method (13th edition, 1999) (7), (8)
The first edition of the Japanese statute for the management of gastric cancer was formulated in 1962, and has been revised several times since then. In June 1999, the Japanese Gastric Cancer Society published the 13th edition of the statute for the management of gastric cancer, which is detailed as follows
T: primary tumor; T1: tumor confined to mucosa (M) or submucosa (SM); T2: tumor invading the muscularis propria (MP) or subplasma tissue (SS); T3: tumor reaching the plasma membrane or penetrating the plasma membrane (SE); T4: tumor directly invading adjacent organs; (invading the greater and lesser omentum, esophagus and duodenum is not called T4; invading the transverse colonic mesentery and reaching the mesentery is called T4); TX: depth of cancer infiltration is unknown.
N: lymph node metastasis, regional lymph nodes were divided into 3 stations; N0: no lymph node metastasis; N1: metastasis to station 1 lymph nodes; N2: metastasis to station 2 lymph nodes; N3: metastasis to station 3 lymph nodes (beyond the regional lymph node metastasis, called distant metastasis M1). (See Table 3)
H: liver metastasis. H0: no liver metastasis; H1: liver metastasis; HX: difficult to determine the presence or absence of liver metastasis.
P: peritoneal metastasis. p0:no peritoneal metastasis;p1:with peritoneal metastasis;px:difficult to determine with or without peritoneal metastasis.
CY: abdominal exfoliative cytology; CY0: no cancer cells were found on abdominal exfoliative cancer cell examination; CY1: cancer cells were found; CYX: no abdominal exfoliative cancer cell examination was done.
M: other distant metastases: including extra-regional lymph nodes, skin, lung, bone, bone marrow, pleura, brain, cerebrospinal membrane and others; M0: no other distant metastases, even if there were liver metastases, peritoneal metastases or positive peritoneal shedding cancer cells; M1: other distant metastases regardless of whether there were liver metastases, peritoneal metastases or peritoneal shedding cancer cells; MX: unknown whether there were other distant metastases.
Table 2 Lymph nodes of different sites of gastric cancer by station
Lymph node group Location LMU/MUL LD/L LM/M/ML MU/UM U E+
MLU/UML
MLU/ UML
1 Cardia right 1 2 1 1 1 1
2 Cardia left 1 M 3 1 1 1
3 lesser curvature 1 1 1 1 1
4sa Gastric short vessels 1 M 3 1 1
4sb Gastric omentum left 1 3 1 1 1
4d Gastric omentum right 1 1 1 1 2
5 Suprapyloric 1 1 1 1 3
6 Subpyloric 1 1 1 1 3
7 Left gastric artery 2 2 2 2 2 2
8a common hepatic artery anterior 2 2 2 2 2 2
8p posterior common hepatic artery 3 3 3 3 3 3
9 Abdominal cavernous artery 2 2 2 2 2 2
10 Splenic hilar 2 M 3 2 2 2
11p proximal splenic artery 2 2 2 2 2 2 2
11d Distal splenic artery 2 M 3 2 2 2
12a hepatoduodenal left 2 2 2 2 2 2 3
12b.p posterior hepatoduodenum 3 3 3 3 3
13 Posterior pancreatic head 3 3 3 M M
14v Superior mesenteric vein 2 2 3 3 M
14a Superior mesenteric artery M M M M M
15 Paracolic vessels of the colon M M M M M
16a1 Aortic fissure M M M M M
16a2.b1 Superior and middle abdominal aorta 3 3 3 3 3
16b2 Inferior abdominal aorta M M M M M
17 Anterior pancreatic head M M M M M
18 Inferior pancreas M M M M M
19 Subphrenic 3 M M 3 3 2
20 Esophageal fissure 3 M M 3 3 1
110 Subthoracic paraesophageal M M M M M M 3
111 Supra-diaphragmatic M M M M M M 3
112 Posterior mediastinum M M M M M M 3
Table 3 GRGCS staging of gastric cancer
N0
N1
N2
N3
T1
IA
IB
II
IV
T2
T2
II
IIIA
IV
T3
II
IIIA
IIIB
IV
T4
IIIA
IIIB
IV
IV
h1, p1, cy1, m1
IV
IV
IV
IV
Advantages: The Japanese gastric cancer staging regarding metastatic lymph node staging is based on the anatomical location of the lymph nodes, thus allowing surgeons to be guided to perform systematic lymph node dissection and reduce the bias of N-staging in TNM staging. (9)
Disadvantages: Because of the complex distribution area of perigastric lymph nodes, it is difficult for surgeons to identify the exact location of each lymph node, so it is limited in practical application. (9) Also, although some studies have reported significant postoperative results for lymph node dissection based on the Japanese lymph node metastasis system, some trials have found that Japanese lymph node dissection surgery
The mortality rate and postoperative complication rate of lymph node dissection in Japan were found to be higher than those of Western surgery. (10)
Modified Dukes’ staging of gastric cancer
In 1994, Adachi et al. applied it to the staging of gastric cancer and proposed the modified Dukes staging, as follows.
Stage A: the cancer is limited to the mucosa, submucosa or intrinsic muscular layer; Stage B: the cancer invades the subplasma layer or plasma layer; Stage Ca: regardless of the depth of tumor infiltration, there are 1-6 lymph node metastases; Stage Cb: regardless of the depth of tumor infiltration, there are more than 7 lymph node metastases.
IV. Summary
As mentioned above, there are two major staging systems for gastric cancer, namely, the TNM staging system developed by the International Union Against Cancer and the staging system developed by the Japanese Society for Gastric Cancer Research. These two staging systems are similar in that they both depend on the growth of the primary tumor, the extent of lymph node involvement, and the presence of distant metastases. The TNM staging system is based on the number of metastatic lymph nodes, whereas the Japanese staging method emphasizes the anatomical location of the involved lymph nodes. These two systems have different roles and were not developed to serve the same purpose. The staging system is very detailed and anatomically based in the Japanese staging method, which guides the surgeon in systematic lymph node dissection and reduces the bias of N-staging in TNM staging, which is its fundamental goal. the TNM system, on the other hand, is mainly used for prognostic guidance, which does not include treatment guidance, and has recently been changed to a number-based N-staging that accurately reflects the metastatic burden as well as the prognosis it provides comparison of outcomes between cohorts provides a simple and reliable method. The scientific validity of the modified Dukes staging, although concise, has yet to be demonstrated in a large case analysis.
References.
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