The large intestine is part of the digestive tract in the abdominal cavity, connecting the small intestine to the anus. The large intestine is divided into the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The main functions of the large intestine are absorption, transportation, and elimination of waste. Malignant tumors that occur in the mucous membrane layer of the large intestine are collectively referred to as colorectal cancer (including colon cancer and rectal cancer). Colorectal cancer ranks second in terms of incidence in developed countries such as Europe and the United States, and fifth in terms of cancer mortality in China.
Colorectal cancer is one of the most common malignant tumors in economically developed countries such as North America and Western Europe, with an annual incidence rate of 30 to 50 per 100,000 population. For example, in Denmark, Luxembourg, and New Zealand, the incidence rate in males can exceed 33 per 100,000 population. According to a report from the United States in 1987, the incidence rate of colorectal cancer in the United States was 30 per 100,000 population, with approximately 152,000 new cases and about 57,000 deaths from the disease each year. It ranks fourth in terms of incidence among malignant tumors and second in terms of mortality.
In addition to North America, the incidence of colorectal cancer is increasing in most regions worldwide. It is estimated that the number of new cases increased by 15.5% from 1985 to 2000, with a 34% increase in developing countries. In some developing Asian, African, and Latin American countries, the incidence rate is relatively low, ranging from 2 to 8 per 100,000 population in countries like India and Colombia. China falls into the intermediate category. In 1977, approximately 37,500 people died from colorectal cancer in China, with an average adjusted mortality rate of 3.54 per 100,000 population, accounting for 5.29% of cancer deaths and ranking sixth in cancer mortality.
From 1990 to 1992, the average adjusted mortality rate for colorectal cancer in China was 454 per 100,000 population, accounting for 4.9% of total cancer deaths and ranking fifth in cancer mortality. Colorectal cancer is generally the fourth to sixth most common malignant tumor in different regions of China. Compared to the 1970s, the death rate from colorectal cancer has increased by approximately 31.95% among urban populations and 8.51% in rural areas due to changes in dietary structure and population aging trends. The incidence of colorectal cancer in Shanghai has more than tripled from the 1960s to the 1980s. High-incidence areas of colorectal cancer in China include the middle and lower reaches of the Yangtze River, Jiangsu, Zhejiang, Shanghai, Fujian, Taiwan, Hong Kong, as well as parts of Northeast and North China. The gender ratio of colorectal cancer in China is nearly equal, with the highest incidence occurring between the ages of 40 and 50.