Gastric cancer is a tumor formed by the malignant transformation of cells in the stomach. Gastric cancer first occurs in the cells of the innermost mucosal layer, and then spreads to the outer layer as the tumor grows. Among the most common malignant tumors worldwide, gastric cancer ranks fourth, and the incidence rate of gastric cancer in China is four to eight times higher than that in Europe and America.
Risk factors of gastric cancer
The occurrence of gastric cancer is influenced by many factors such as age, diet and stomach diseases. The risk factors of gastric cancer include
(1) Some gastrointestinal pathologies, such as Helicobacter pylori infection in the stomach, chronic gastritis, pernicious anemia, intestinal chemosis, familial adenomatous polyposis or gastric adenoma;
(2) Intake of more pickled and smoked foods and less fruits and vegetables;
(3) Food is not handled and stored properly;
(4) Advanced age, male; smoking;
(5) Immediate family member suffering from stomach cancer.
Symptoms of Stomach Cancer
Early stage gastric cancer may cause non-specific symptoms such as indigestion and stomach discomfort, bloating after eating, nausea, loss of appetite, heartburn, etc. Symptoms of progressive gastric cancer include blood in stool, vomiting, unexplained weight loss, stomach pain, jaundice, ascites, discomfort or difficulty in swallowing.
The following tests are commonly used to detect and diagnose gastric cancer
1.Physical examination and inquiry about previous health condition, medical history and treatment, pay attention to the presence of masses;
2.Blood routine, blood biochemistry and tumor marker test in blood.
3.Endoscopy and biopsy of gastrointestinal tract, which can observe the internal situation of esophagus, stomach and duodenum directly, and use biopsy forceps to “bite” part of the tumor tissue under the direct view of endoscope, or use a small brush to take off tumor cells under the microscope to confirm whether there are cancer cells.
4.Fecal occult blood test: taking a small amount of stool specimen for laboratory test can detect a small amount of bleeding in gastrointestinal tract.
5.Barium meal imaging of upper gastrointestinal tract: the liquid containing barium that the patient drinks into adheres to the esophagus and stomach wall, which is picked up and imaged by X-ray.
6.CT scan and ultrasonic examination to understand whether there are metastases in liver, abdominal lymph nodes, lung, etc.
Staging of gastric cancer
After the diagnosis of gastric cancer is confirmed, the process of clarifying whether the tumor is confined to the stomach or has spread to other parts through further examination is called staging. The clinical staging is based on the results of physical examination and imaging examination, and the accurate pathological staging can be made after surgery according to the depth of tumor invasion to the stomach wall (T), lymph node metastasis (N) and distant metastasis (M). The prognosis of gastric cancer mainly depends on the staging, and accurate staging is crucial to guide the treatment. Although surgical pathology is the most accurate staging method, advances in imaging technology have led to great improvements in clinical staging, and commonly used examination methods include chest X-ray, endoscopy and endoscopic ultrasound, CT scan and laparoscopy. About half of the patients have exceeded the local extent at the time of diagnosis, and local lymph node metastasis can be found in nearly 70% to 80% of resected specimens of gastric cancer. In locally advanced and metastatic gastric cancer, those with poor physical status, liver metastasis, abdominal metastasis and alkaline phosphatase ≥100 U/L have poor prognosis.
Regional lymph nodes(N)
Number of metastases
N0
0
N1
1 to 6
N2
7 to 15
N3
>15
Distant metastasis(M)
M0
No distant metastasis
M1
With distant metastasis
Staging (TNM)
Stage 0
Tis,N0,M0
Stage IA
T1,N0,M0
IB period
T1,N1,M0;T2,N0,M0
Phase II
T1,N2,M0;T2,N1,M0;T3,N0,M0
Phase IIIA
T2,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
Treatment of gastric cancer
The results of a large number of clinical studies show that comprehensive treatment is the fundamental guarantee to improve the efficacy, which requires close cooperation among specialists in the disciplines of surgical oncology, medical oncology, radiotherapy, radiology and pathology, preferably with a consensus before any treatment is started, to determine the best long-term treatment planning on the basis of adequate staging.
1. Those whose tumors can be resected and who are in good health (more than half of the cases).
・Pre-operative clinical staging of T1 or less is treated by direct surgery;
・T2 or T2 or above can be treated with chemotherapy or chemoradiotherapy followed by surgery in addition to direct surgery.
After surgery, the next treatment is decided according to pathology.
・T1N0: No further treatment is needed, follow up;
・T2N0: No further treatment, but also postoperative chemotherapy (fluorouracil-based) if the tumor is hypodifferentiated, lymphovascular infiltration, nerve infiltration, or younger than 50 years old;
・T3, T4, or any T when there is lymph node metastasis, or tumor residual after surgery (microscopic or visual findings): all give chemoradiotherapy → chemotherapy (fluorouracil-based sensitizing radiotherapy and follow-up chemotherapy), or combined chemotherapy (those who had ECF before surgery still use this regimen for 3 cycles of chemotherapy after surgery).
2. If the tumor is unresectable, or if the patient is in poor physical condition and cannot be operated.
・Chemical radiotherapy: radiotherapy + fluorouracil-based sensitizing chemotherapy
・chemotherapy, palliative treatment
Radiotherapy for gastric cancer is more frequently done in the United States. Radiotherapy for gastric cancer has high requirements for simulated positioning, treatment planning and target area setting. The dose of radiotherapy is 45-50,4Gy (1,8Gy per day).
3. Once metastasis is detected, palliative treatment should be given no matter at the beginning or during the course of treatment.
Chemotherapy is the most effective palliative treatment, suitable for those who can get out of bed for more than half a day during the day.
Other treatments: nutritional support (enteral nutrition and nutritional guidance), relief of obstruction (stenting, laser, radiotherapy or surgery), pain control (radiotherapy and/or drugs) and hemostasis (radiotherapy, surgery or endoscopic treatment).
Chemotherapy
1. Adjuvant chemotherapy before and after surgery
In perioperative chemotherapy before and after surgery, epi-amycin/cisplatin/5-fluorouracil (ECF) and its modified regimens can significantly prolong disease-free survival and overall survival; postoperative adjuvant chemotherapy based on fluorouracil analogs (Tegeo, S1) can also benefit patients.
2.Progressive stage or relapse
The results of a large number of clinical studies show that chemotherapy can make about half of the patients obtain significant efficacy and can improve the quality of life and prolong survival. Commonly used regimens include: docetaxel/cisplatin/5-fluorouracil (DCF) and its modified regimen, ECF and its modified regimen, cisplatin/5-fluorouracil, epi-amycin/oxaliplatin/capecitabine. Other drugs: irinotecan, paclitaxel and tegeo, etc.
Surgery
Surgery is the primary treatment for gastric cancer, aiming for complete resection with adequate margins (5 cm), requiring removal of at least the first station of gastric lymph nodes, and no less than 15 lymph nodes should be removed. The aim of surgery is to achieve a radical resection without microscopic residuals; however, radical resection is not possible in approximately 50% of patients with focal gastric. Even with radical resection, 60% of patients still have local recurrence or distant metastases, and combined chemotherapy and radiotherapy can improve the outcome.
Commonly used procedures are: subtotal gastrectomy, distal gastrectomy, and total gastrectomy.
Follow-up and monitoring
All patients with gastric cancer should be followed up systematically. The follow-up includes comprehensive medical history and physical examination every four to six months for the first three years and annually thereafter. Routine blood tests, blood biochemistry, endoscopy and imaging tests should also be checked according to clinical conditions. In patients with subtotal or total gastric resection, serum B12 levels, iron and calcium levels should be monitored, and B12 can be injected once a month. iron absorption rate decreases in the absence of gastric acid, and oral iron supplements are best combined with acidic beverages. Calcium supplementation is encouraged.
Anemia should be prevented after major gastrectomy
The normal human gastrointestinal tract absorbs about 2 micrograms of vitamin B12 per day, and its absorption depends on the presence of endogenous factors and intact ileal receptors. Endoglin is a mucopolysaccharide protein secreted into the gastric juice by the mucosal cells of the gastric pylorus and has a special affinity for vitamin B12. When food containing vitamin B12 enters the stomach, it rapidly binds to the internal factor to form a complex, which is absorbed by the epithelial cells of the intestinal mucosa when it reaches the lower ileum. When a major gastric resection is performed, the absorption of vitamin B12 is affected due to the lack of endoglin, which in turn produces megaloblastic anemia. In addition, some patients develop iron deficiency anemia because the food does not pass through the duodenum but directly into the jejunum, which affects the absorption of iron. Once megaloblastic anemia occurs, vitamin B12 can be given intramuscularly at 100 micrograms daily for 14 days, and then twice a week for 4 weeks until hemoglobin and red blood cells return to normal. For those who have not yet developed anemia but have low serum vitamin B12 level, 250 micrograms of vitamin B12 can also be injected every 4 weeks or 1000 micrograms every 2 to 3 months. For iron deficiency anemia, iron dextrose complex or iron sorbitol citrate complex can be injected with satisfactory results.
Other tumors of the stomach
Gastric mesenchymal tumor is a tumor originating from connective tissue supporting cells with a younger age of onset and a different clinical presentation and treatment than gastric cancer. Gastric mucosa-associated lymphoma has a better prognosis and should not be surgically resected. Anti-H. pylori, radiotherapy and chemotherapy are the main treatments.