What is the pathogenesis of colon cancer

Colon cancer is one of the common malignant tumors, with the highest incidence in the 40-50 age group. According to the world epidemiological survey, the incidence of colon cancer is highest in North America, Western Europe, Australia, New Zealand and other places, ranking first and second among visceral tumors, but the incidence is very low in Asia, Africa, Latin America and other places. The incidence and mortality rate in my country are lower than those of common malignant tumors such as gastric cancer, esophageal cancer and lung cancer.

Data from various places in recent years show that with the improvement of people's living standards and changes in dietary structure, the incidence rate has been increasing year by year. The incidence rate of colorectal cancer in China and Japan is significantly lower than that in the United States, but the first generation of immigrants to the United States can see an increase in the incidence rate of colorectal cancer, and the second generation is basically close to the incidence rate of Americans. From an epidemiological point of view, the incidence of colon cancer is related to the environment, living habits, and especially the diet. It is generally believed that high-fat diets and insufficient fiber are the main causes of the disease. Studies have shown that a diet with saturated fatty acids can increase the concentration of bile acids and neutral sterols in the colon and change the composition of the coliform flora. Bile acids can generate carcinogens such as 3-methylcholanthrene through bacterial action, and sterol rings can also be aromatized by bacteria to form carcinogens. Dietary fiber includes cellulose, pectin, hemicellulose, lignin, etc., which absorbs water, increases the amount of feces, dilutes the concentration of intestinal residues, and can shorten the time for feces to pass through the large intestine and reduce the time for carcinogens to contact the intestinal mucosa. If dietary fiber is insufficient, it is already one of the causes of colon cancer.

Chronic colorectal inflammation, such as ulcerative colitis, has a higher incidence of colorectal cancer than the general population. During the development of inflammatory proliferative lesions, polyps can often form and further develop into colorectal cancer. In Crohn's disease, those with colon and rectum involvement may develop into cancer. There is a significant difference in the incidence and mortality of colorectal cancer between schistosomiasis-endemic areas and non-endemic areas. In the past, it was believed that patients with chronic schistosomiasis had chronic ulcers and inflammatory polyps in the colorectal mucosa due to the deposition of schistosome eggs and toxin stimulation in the intestinal wall, which in turn caused cancer. This view has been debated. According to the gradual control of schistosomiasis in Jiashan County, Zhejiang Province, the number of new cases has decreased significantly, and patients in the late stage tend to disappear, while the incidence of colorectal cancer is still very high. According to general data statistics, the incidence of colorectal cancer in patients with colorectal polyps is 5 times that of patients without colorectal polyps. The incidence of cancer in familial multiple intestinal polyposis is even higher. In recent years, there have been reports of families with positive colorectal cancer, and their incidence is four times that of the general population, indicating that genetic factors may be involved in the occurrence of colorectal cancer.