Screening of natural population has been documented that mass screening with an interval of 1.5-2 years can help detect early gastric cancer. For example, in Japan, the medical profession adopts the air-barium double contrast method of radiological imaging for screening, and then performs gastroscopic precision examination on suspicious cases, resulting in an early surgery rate of gastric cancer of over 50% and a 5-year survival rate of over 90%. At present, China mainly conducts selective local screening in areas with high incidence of gastric cancer, such as age over 35 years old, poor dietary habits such as consuming high salt and moldy food, family history of tumor, etc., and then selects high-risk individuals by comprehensive analysis, and then conducts endoscopy and X-ray radiography. Comprehensive census results from all over China show that the detection rate of gastric cancer in census is about 0.037-0.6%, and early gastric cancer accounts for 15-25% of the detected gastric cancer, which greatly improves the detection rate of gastric cancer in asymptomatic patients. According to statistics, about half of the asymptomatic gastric cancer patients are confirmed to be early gastric cancer by surgical pathology, and most of them have no lymph node metastasis; while 57% of symptomatic gastric cancer have already had lymph node metastasis. Therefore, the screening of natural population is a difficult and important task. Outpatient screening is an important part of early diagnosis of gastric cancer, as anyone who comes to the clinic with relevant symptoms will be screened. Early gastric cancer is characterized by symptoms such as hidden pain in the upper abdomen, bloating, loss of appetite, nausea and vomiting. These symptoms are not unique to early gastric cancer, so they are easily ignored as general gastric diseases, which is one of the reasons why patients are diagnosed too late. Therefore, it should be emphasized that men over 40 years old (relaxed to 35 years old for smokers and alcoholics) should be screened for any slight upper abdominal discomfort for the purpose of early detection and diagnosis. In addition, if the symptoms of dyspepsia are obvious and persist for a long time, and the symptoms do not improve significantly after clinical treatment, the possibility of gastric cancer should be considered. For those who have chronic atrophic gastritis, pernicious anemia, gastric polyps, residual stomach and benign gastric ulcer, they should be more alert to the evolution of gastric cancer. The detection rate of early gastric cancer by outpatient screening in China is 0.27%, which is lower than that in Japan (0.88%) and between that in Western Europe (0.37%) and the United States (0.1%). It is now generally accepted that gastroscopy is the best screening method for early gastric cancer. High-risk groups include those with precancerous status and precancerous lesions. The former refers to some diseases with significantly higher risk of gastric cancer, such as chronic atrophic gastritis, gastric ulcer, gastric polyp, remnant stomach, giant gastric mucosal crepitus disease, etc. The latter mainly refers to pathological atypical hyperplasia of gastric mucosa. The detection rate of gastric cancer and early gastric cancer by high-risk group follow-up method is higher than that by census method and outpatient screening method. Nowadays, the natural course of gastric cancer is considered to be a slow process, which takes about 3-4 years to develop from the early stage to the progressive stage. Therefore, it is more appropriate to follow up and review gastroscopy every 6-12 months for high-risk groups. It is widely accepted that H. pylori infection is associated with gastric cancer. It has been shown that the risk of gastric cancer is 3-6 times higher in H. pylori-infected individuals than in uninfected individuals. It is not clear whether treatment of H. pylori infection can prevent gastric cancer, but H. pylori-infected individuals with a family history of malignant gastric disease and clinical symptoms should be classified as a high-risk group for gastric cancer, and follow-up studies should be conducted, with interventional treatment if necessary. Early signs and common symptoms of gastric cancer Gastric cancer is a common malignant tumor, and the age of prevalence is just between 50 and 60 years old, so it is a “roadblock” for human beings to enter the old age. So, how can stomach cancer be detected early? Stomach cancer is quietly mixed with many stomach diseases, so it is not easy to detect it at an early stage. Especially, the early symptoms of stomach cancer are similar to many other stomach diseases, so even if you seek medical help, you may not think it is cancer, thus delaying the disease and missing the time for early treatment. According to medical researchers, early signs of gastric cancer include: 1. inexplicable loss of appetite or upper abdominal discomfort; 2. frequent distension of upper abdomen, which is relieved after repeated warming and is especially obvious after eating; 3. irregular vague pain or transient colic in upper abdomen; 4. nausea, constipation or diarrhea after eating too much; 5. abnormal aversion to meat; 6. unexplained weight loss, body fatigue and weakness; 7. Mild anemia for which no reason can be found. One or several of these signs may occur repeatedly within a certain period of time. What’s more, when these signs are found and mistaken for general gastric disease and the symptoms do not ease after treatment, you should be extra vigilant, it may be stomach cancer! It is worth mentioning that if a possible precancerous lesion such as chronic gastritis or gastric ulcer turns into gastric cancer, one of the obvious features of the early signs is that the pattern or symptoms of the original gastric disease have changed to a larger extent. The common symptoms of stomach cancer include stomach pain, loss of appetite, weight loss, nausea, vomiting, acid reflux, heartburn, bleeding, black stool, diarrhea, etc. Patients with these symptoms should go to hospital for examination and treatment in time.