What are the early symptoms of colon cancer? Can colon cancer be cured? How long can you live?

Colon cancer is a common malignant tumor of the digestive tract, ranking second among gastrointestinal tumors. The most common sites are the rectum and the junction of the rectum and the sigmoid colon, accounting for 60%. The disease mostly occurs after the age of 40, with a male to female ratio of 2:1. The incidence of colon cancer is mainly related to a high-fat and low-fiber diet. Chronic inflammation of the colon makes the incidence of colon cancer higher than that of the general population. The incidence of colon cancer in people with colon polyps is 5 times that of those without colon polyps. Familial multiple intestinal polyposis has a higher incidence of cancer. Genetic factors may also be involved in the onset of colon cancer. The early symptoms of colon cancer are obvious, and in the middle and late stages, it may manifest as abdominal distension and indigestion, followed by changes in bowel habits, abdominal pain, and mucus or bloody stools. After tumor ulceration, blood loss, and toxin absorption, symptoms such as anemia, low fever, fatigue, weight loss, and lower limb edema often occur. Colon cancer can be surgically removed in the early stage, but the recurrence rate after surgical resection is high. Therefore, the best method is to combine traditional Chinese and Western medicine for early stage colon cancer. Surgical removal of tumor lesions and holistic treatment of traditional Chinese medicine can remove residual cancer cells and prevent recurrence and metastasis. For patients who cannot undergo surgery in the middle and late stages or are older and weak, traditional Chinese medicine and Chinese herbal medicine are mainly used to control the development of the disease and gradually treat it, ultimately achieving the goal of living with the tumor. 1. Medical history and symptoms Changes in bowel habits or stool characteristics, most of which are manifested as increased frequency of bowel movements, unformed or loose stools, blood and mucus in the stool, sometimes constipation or diarrhea alternating with constipation, thinner stools, pain in the middle and lower abdomen, varying degrees of severity, mostly dull pain or bloating. Patients with right-sided colon cancer often find abdominal masses. Pay attention to systemic symptoms such as greed for blood, weight loss, fatigue, edema, and hypoproteinemia. When the tumor is necrotic or secondary infection occurs, the patient often has a fever. 2. Physical examination reveals palpable abdominal masses or masses found during digital intestinal examination. The masses are usually hard and accompanied by tenderness, irregular shapes, anemia, weight loss, cachexia, and those with lymph node metastasis may cause ascites, lower limb edema, jaundice, etc. by compressing venous return. Colon cancer is more common in middle-aged and elderly people, with the majority aged 30 to 69, more in men than in women. Early symptoms are usually not obvious. Common symptoms in middle and late stage patients include abdominal pain and digestive tract irritation symptoms, abdominal masses, changes in bowel habits and stool characteristics, anemia and symptoms caused by chronic toxin absorption, intestinal obstruction, intestinal perforation, etc. 1. Symptoms (1) Abdominal pain and digestive tract irritation symptoms Most patients experience varying degrees of abdominal pain and discomfort, such as dull abdominal pain, right-sided abdominal fullness, nausea, vomiting, and loss of appetite. Symptoms often worsen after eating, sometimes accompanied by intermittent diarrhea or constipation. They are easily confused with common chronic appendicitis, ileocecal tuberculosis, ileocecal segmental enteritis, or lymphoma in the right lower abdomen. Hepatic flexure cancer of the colon may present as paroxysmal colic in the right upper abdomen, similar to chronic cholecystitis. It is generally believed that pain in right-sided colon cancer often reflects to the upper part of the navel; pain in left-sided colon cancer often reflects to the lower part of the navel. If the tumor penetrates the intestinal wall and causes local inflammatory adhesions, or forms a local abscess after chronic perforation, the pain site is the site of the tumor. (2) Abdominal masses are generally irregular in shape, hard in texture, and nodular in surface. Transverse colon and sigmoid colon cancers have a certain degree of mobility and mild tenderness in the early stage. If ascending and descending colon cancers have penetrated the intestinal wall and adhered to surrounding organs, chronic perforation to form abscesses, or pierced adjacent organs to form internal fistulas, the masses are mostly fixed, with unclear edges and obvious tenderness. (3) Changes in bowel habits and stool characteristics are the result of ulcers formed by tumor necrosis and secondary infection. Bowel habits change due to toxin stimulation of the colon, the number of bowel movements increases or decreases, and sometimes diarrhea and constipation alternate. There may be abdominal cramps before defecation, which are relieved after defecation. If the tumor is located lower or in the rectum, there may be anal pain, difficulty in defecation or tenesmus and other rectal irritation symptoms. The stool is often unformed and mixed with mucus, pus and blood. Sometimes it contains a large amount of blood and is often misdiagnosed as dysentery, enteritis, hemorrhoidal bleeding, etc. (4) Symptoms of anemia and chronic toxin absorption. Necrosis and ulceration on the surface of the tumor may cause persistent small amounts of bleeding. The blood mixed with feces is not easy to attract the patient's attention. However, chronic blood loss, toxin absorption and malnutrition may cause anemia, emaciation, weakness and weight loss. Late-stage patients may have edema, hepatomegaly, ascites, hypoproteinemia, cachexia and other phenomena. If the tumor penetrates the stomach and bladder to form an internal fistula, corresponding symptoms may also occur. (5) Intestinal obstruction and intestinal perforation are caused by mass filling in the intestinal cavity, strangulation of the intestine itself or adhesion and compression outside the intestinal cavity. They are often manifested as slowly progressive incomplete intestinal obstruction. Patients in the early stages of obstruction may have chronic abdominal pain accompanied by abdominal distension and constipation, but they can still eat. The symptoms are more severe after eating. Symptoms can be relieved after treatment with laxatives, colon cleansing, Chinese medicine, etc. After a long period of repeated attacks, the obstruction gradually becomes complete. Some patients present with acute intestinal obstruction. In acute colon obstruction in the elderly, about More than half of them are caused by colon cancer. When the colon is completely obstructed, the ileocecal valve blocks the colon contents from flowing back to the ileum, forming a closed loop intestinal obstruction. The colon from the cecum to the obstruction site can be extremely dilated, and the intraluminal pressure continues to increase, rapidly developing into strangulated intestinal obstruction, or even intestinal necrosis and perforation, causing secondary peritonitis. Some patients have atypical symptoms in the past, making it difficult to make a clear diagnosis before surgery. Cancers located in the cecum, transverse colon, and sigmoid colon can cause intussusception when the intestines move violently. Patients with colon cancer do not necessarily have the above typical symptoms. Their clinical manifestations are related to the location of the tumor, the pathological type, and the duration of the disease. The colon can be divided into left and right halves with the splenic flexure of the colon as the boundary. The two halves are different in terms of embryonic origin, blood supply, anatomical and physiological functions, intestinal content characteristics, and common cancer types, so there are obvious differences in clinical manifestations, diagnostic methods, surgical methods, and prognosis. The embryonic origin of the right colon is the midgut, with a larger intestinal cavity and liquid intestinal contents. One of its main functions is to absorb water. Cancers are mostly lumpy or ulcerative, with easy bleeding on the surface. Toxins produced by secondary infection are easily absorbed. The three common main symptoms are right anterior abdominal and digestive tract irritation symptoms, abdominal masses, anemia, and manifestations of chronic toxin absorption, and the chance of intestinal obstruction is less. The embryonic origin of the left colon is the hindgut, with a thinner intestinal cavity and solid intestinal contents. Its main function is to store and discharge feces. Cancers are mostly invasive and can easily cause circular strangulation of the intestinal cavity. The three common main symptoms are changes in bowel habits, bloody stools, and intestinal obstruction. Intestinal obstruction can manifest as sudden acute complete obstruction, but most are chronic incomplete obstruction, with obvious abdominal distension, thin stools like pencils, and progressive worsening of symptoms that eventually develop into complete obstruction. Of course, this distinction is not absolute, and sometimes there are only 1 to 2 clinical manifestations. 2. Signs and symptoms found in physical examination may vary according to the course of the disease. Early patients may have no positive signs. Patients with a longer course of the disease may have palpable masses in the abdomen, and may also have signs of weight loss, anemia, and intestinal obstruction. If the patient has intermittent abdominal "gas-like" masses, accompanied by colic and hyperactive bowel sounds, the possibility of colon cancer causing adult intussusception should be considered. If left supraclavicular lymphadenopathy, hepatomegaly, ascites, jaundice, or pelvic masses are found, they are mostly late manifestations. There is tenderness in the liver, lung, and bone metastases. Rectal digital examination is an indispensable examination method. Generally, it can understand whether there are polyps, masses, and ulcers within 8 cm from the anus. Low-positioned sigmoid colon cancer can be palpated through the abdomen and rectal bimanual examination. At the same time, attention should be paid to whether there are metastatic masses in the pelvis. Female patients can undergo abdominal, rectal, and vaginal triple examinations. The basic premise of colon cancer treatment is to have a comprehensive and correct tumor diagnosis. The diagnosis of tumors is based on comprehensive medical history, physical examination, and related instrument examinations. The general preoperative diagnosis mainly includes tumor conditions and other systemic conditions. Risk factors Clinically, some factors may greatly increase the risk of disease, including: 1. Age of onset. Most patients develop after the age of 50. 2. Family history: If a person's first-degree relatives, such as parents, have had colorectal cancer, his risk of developing the disease in his lifetime is 8 times higher than that of the general population. About a quarter of new patients have a family history of colorectal cancer. 3. History of colon disease: Certain colon diseases such as Crohn's disease or ulcerative colitis may increase the chance of colorectal cancer. Their risk of colon cancer is 30 times that of ordinary people. 4. Polyps: Most colorectal cancers develop from small precancerous lesions, which are called polyps. Among them, villous adenomatous polyps are more likely to develop into cancer, with a chance of malignant transformation of about 25%; tubular adenomatous polyps have a malignant transformation rate of 1-5%. 5. Genetic characteristics: Some familial tumor syndromes, such as hereditary non-polyposis colon cancer, can significantly increase the chance of developing colorectal cancer, and the onset time is younger. Some epidemiological studies on colon cancer have shown that social development status, lifestyle and dietary structure are closely related to colon cancer, and there are phenomena suggesting that there may be differences in environmental and genetic factors affecting the incidence of colon cancer in different parts and age groups. Environment (especially diet), genetics, physical activity, occupation, etc. are possible etiological factors affecting the incidence of colon cancer. Epidemiological studies on dietary factors have shown that 70% to 90% of tumor incidence is related to environmental factors and lifestyle, and 40% to 60% of environmental factors are related to diet and nutrition to a certain extent. Therefore, dietary factors are considered to be extremely important factors in the incidence of tumors. 1. The mechanism of action of high fat, high protein and low cellulose can be summarized as follows: ① It affects intestinal lipid metabolism. A high-fat diet increases the activity of 7a-dehydroxylase, leading to an increase in the formation of secondary bile acid, while cellulose has the opposite effect. It reduces the concentration of deoxybile acid in the intestine and increases the solid phase in the feces by inhibiting reabsorption, dilution, adsorption and chelation, promoting excretion; some dietary factors (such as calcium ions) can reduce the levels of intestinal ionized fatty acids and free bile acids, both of which have a damaging effect on the intestinal epithelium; inhibit the degradation of intestinal cholesterol. Milk, lactose and galactose have the effect of inhibiting the redox of bile ane. ② Cellulose also has the effect of changing intestinal flora, affecting the structure and function of intestinal mucosa, affecting the growth rate of mucosal epithelial cells, regulating intestinal pH, and strengthening the mucosal barrier through mucin, reducing the damage of intestinal toxic substances to the intestinal epithelium; ③ High fat and some carbohydrates can increase the activity of intestinal cell enzymes (such as glucuronidase, ornithine dehydroxylase, nitroreductase, azooxidase, lipoxygenase, cyclooxygenase), and promote the production of carcinogens and co-carcinogens. ④ The influence of biological macromolecule activity. When the cytoplasm is acidified, DNA synthesis is inhibited and the cell cycle is prolonged. 2. Vitamins: Case-control studies have shown that carotene, vitamin B2, vitamin C, and vitamin E are all related to reducing the relative risk of colon cancer, and the relationship is dose-response. Vitamin D and calcium have a protective effect. 3. Onions and garlic: The protective effect of onion and garlic foods on the body has been widely recognized, and the inhibitory effect of this type of food on tumor growth has been confirmed many times in experiments. Garlic oil can significantly reduce the damage to colon mucosal cells caused by dimethylcholanthrene, and can reduce the induction rate of colon cancer in mice by 75%. The results of a case-control study showed that the risk of colon cancer in people with high garlic intake was 74% of that in the low-intake group. 4. Salt and pickled foods: The relationship between salt intake and gastric cancer, colon cancer, and rectal cancer. The relative risks of the three cancers in the high-salt intake group were all increased. The results of a case-control study showed that the excess risk of colon cancer in those who consumed pickled foods more than three times a week was 2.2 times that of those who consumed pickled foods less than once (P55 years old group) and 6 times that of the family. Family members (first-degree relatives) with a family history of colon cancer, especially those with a colon cancer onset age of under 40, should be given great attention. Disease factors 1. Intestinal inflammation and polyps: Chronic intestinal inflammation and polyps, adenomas, and those with extensive ulcerative colitis for more than 10 years: The risk of developing colon cancer is several times higher than that of the general population. The chance of patients with ulcerative colitis with severe atypical hyperplasia developing colon cancer is about 50%. Obviously, ulcerative colitis Patients have a higher risk of developing colon cancer than the general population. Data from my country indicate that those who have been ill for more than 5 years have a 2.6 times higher risk of developing colon cancer than the general population, but the relationship with rectal cancer is not close. For those with localized lesions and intermittent onset, the risk of developing colon cancer is lower. Crohn's disease is also a chronic inflammatory disease that often invades the small intestine and sometimes involves the colon. There is increasing evidence that Crohn's disease is associated with the occurrence of colon and small intestinal adenocarcinoma, but not to the same extent as ulcerative colitis. 2. Schistosomiasis: Based on a retrospective survey of cancer deaths in Zhejiang Province from 1974 to 1976, the survey data on malignant tumors in China from 1975 to 1978, and the Chinese Schistosomiasis Atlas, the correlation between schistosomiasis endemic areas and the incidence and mortality of colon cancer was explored. Twelve provinces and cities in southern my country There is a very significant correlation between the incidence of schistosomiasis and the mortality rate of colorectal cancer in 10 counties in the autonomous region and Jiaxing area of ​​Zhejiang Province. This suggests that schistosomiasis may be related to the high incidence of colorectal cancer in areas of my country where schistosomiasis is severely prevalent. However, there is little evidence from epidemiological studies that colon cancer is related to schistosomiasis. For example, in Jiashan County, Zhejiang Province, where schistosomiasis is now under control, the mortality rate of colon cancer and the incidence of schistosomiasis in this area were once the highest in my country, and the schistosomiasis infection rate has dropped significantly. However, according to survey results in recent years, epidemiological and pathological research reports on the canceration of colon polyps also believe that the canceration of polyps has nothing to do with the presence or absence of schistosome eggs in the polyps. In addition, the results of the population colon cancer surveys conducted in the above two areas do not support that schistosomiasis is a risk factor for colon cancer. Cases The results of the control study did not find a correlation between the history of schistosomiasis and the incidence of colon cancer. 3. Cholecystectomy: In recent years, there have been more than 20 articles in my country discussing the relationship between cholecystectomy and the incidence of colon cancer. Some of these studies have shown that cholecystectomy can increase the risk of colon cancer, especially proximal colon cancer. The risk of colon cancer in men increases after cholecystectomy; on the contrary, the risk of rectal cancer in women decreases after the operation. There is also a view that the impact of cholecystectomy on colon cancer in women is greater than that in men. It is generally believed that the occurrence of tumors is the result of the combined action of multiple factors, and colon cancer is no exception. As a disease closely related to the lifestyle of Western society, colon cancer is also closely related to it in its etiology, and it is believed that dietary factors play the most important role. At present, the etiology model of "high fat, high protein, high calories and lack of fiber intake" is still dominant, and most research results are consistent with this model. Some other carcinogenic factors are relatively weak, such as disease factors, genetic factors, occupational factors, etc. It can be considered that the carcinogenic process of colon cancer is mainly based on the role of dietary factors, combined with the multi-link joint action of some other factors. With the deepening of etiological research and the penetration of multiple disciplines, new understandings have been gained on the carcinogenic mechanism of colon cancer in the etiological hypothesis. In the field of epidemiology, modern technology is more widely used to gain a deeper understanding of some factors that were inconsistent with previous results, and the possible causes suggested by the epidemiological results will be further clarified. According to the multi-stage theory of carcinogenesis, the occurrence of colon cancer also goes through three stages: initiation, promotion, and progression. Morphologically, it is manifested as normal mucosa → hyperplasia → adenoma formation → adenoma carcinoma → infiltration and metastasis. For example, taking the carcinogenesis of familial adenomatous polyposis as a model, the natural history of colon cancer can be as long as 10 to 35 years. This provides a very favorable opportunity for the prevention of colon cancer. According to different intervention measures at different stages of the natural history of colon cancer, my country has formulated the following prevention strategies. 1. Primary prevention Before the tumor occurs, eliminate or reduce the exposure of the colon mucosa to carcinogens, inhibit or block the carcinogenesis of epithelial cells, and thus prevent the occurrence of tumors. These measures include dietary intervention, chemical prevention and treatment of precancerous lesions. (1) Dietary intervention British scholar Burkitt pointed out long ago that colon cancer is a "modern disease" related to modern lifestyle and diet. A large number of epidemiological studies, especially immigrant epidemiological studies, have shown that the incidence of colon cancer is related to excessive energy intake, obesity, excessive saturated fatty acid intake, reduced physical activity, and insufficient intake of dietary fiber and micronutrients (vitamins A, E, C, trace elements selenium and calcium). In terms of dietary intervention, dietary fiber has been the most studied. As early as the 1960s and 1970s, Burkitt discovered that colon cancer was very rare in black Africans, and that the diet of African aborigines contained a lot of dietary fiber, so he proposed the hypothesis that a high-fiber diet is a protective factor for colon cancer. Subsequently, a large number of studies have shown that dietary fiber can dilute or absorb carcinogens in feces, speed up the passage of food residues in the intestine, and thus reduce the exposure of the intestinal mucosa to carcinogens in food. At the same time, dietary fiber can also play a protective role against colon cancer by changing the metabolism of bile acid, lowering the pH value of the colon, and increasing the production of short-chain fatty acids. Early observational epidemiological studies and case-control studies have shown that the protective effect of dietary fiber on colon cancer increases with the increase in intake. For example, Howe collected data from 13 case-control studies with a total of 5,287 patients and 10,470 controls, and found that 12 of the studies supported the negative correlation between dietary fiber intake and the incidence of colon cancer; it was also found that after adjusting for confounding factors, the intake of vitamin C and beta-carotene was only slightly negatively correlated with the incidence of colon cancer. In view of the fact that in prospective clinical intervention trials, if the occurrence of colon cancer is used as the "end-point", long-term follow-up is required to draw a clear conclusion. Therefore, some people advocate the use of the occurrence (or recurrence) of precancerous lesions-adenomas as an evaluation indicator of colon cancer risk. In recent years, some "intermediate markers" have been advocated to evaluate the effect of intervention, in order to greatly shorten the time required for intervention trials. The most commonly used intermediate index is the rectal mucosal crypt tritium-labeled thymidine nucleoside (HTdR) incorporation index (LI), which reflects the proliferation status of cells. Studies have confirmed that LI is associated with the risk of colon cancer and has been widely used in the evaluation of dietary intervention trials. In recent years, immunohistochemical tests for detecting the incorporation rate of brominated deoxyuridine nucleoside (Br-UdR) and proliferating cell nuclear antigen (PCNA) have been established. These tests can also reflect the proliferation status of cells without the use of radionuclides. Other intermediate indicators used for evaluation include abnormal crypts and microadenomas found under microscopy, as well as protein kinase C (PKC) and ornithine decarboxylase (ODC) activities. For example, Alberts et al. added 13.5 g/d of wheat bran fiber to the diet of a group of 17 patients without tumors after colon cancer surgery. Using rectal crypt LI as an indicator, they observed that LI decreased significantly in 6 of the 8 patients with high LI, and the total decrease rate for the whole group was 22% (P11 g/d of wheat bran) can reduce the recurrence of adenoma, while vitamin C (4 g/d) and vitamin E (400 mg/d) have no such effect. However, large-sample prospective trials completed in recent years have failed to confirm the protective effect of dietary fiber. Schatzkin et al. reported that 2079 patients with a history of colon cancer were randomly divided into 2 groups. One group received dietary counseling and accepted a low-fat, high-fiber diet, and the other group maintained a regular diet and did not receive counseling. After 1 to 4 years, colonoscopy found that there was no difference in the recurrence rate of colon adenocarcinoma in the two groups. A randomized controlled study recently completed by Albert et al. in Arizona, USA, showed that 1,429 patients with a history of colorectal adenoma were given a low-fiber (2.0 g of wheat bran added/d) or high-fiber (13.5 g of wheat bran added/d) diet, and the recurrence rate of colorectal adenoma in the two groups of patients was the same. A large-sample prospective cohort study conducted by Fuchs and Giovannucci et al. also supports the above results. This is a health survey of 121,700 registered nurses (all female) in the United States that began in 1976. Since 1980, the dietary status of each woman has been investigated in the form of a questionnaire, and 88,757 subjects who met the research criteria (34 to 59 years old) were followed up until 1996. In the 16 years, this group of study subjects had 787 cases of colon cancer, and 27,530 people underwent colonoscopy, and 1,012 cases of colorectal adenoma were found. After analyzing the above data and adjusting for age, total energy intake and other known risk factors, it was found that dietary fiber intake had no correlation with the risk of colon cancer. The relative risk of colon cancer was 0.95 (95% CI: 0.73-1.25) when comparing the highest and lowest 20% quantiles of fiber intake. Similarly, no correlation was found between dietary fiber intake and the occurrence of colon cancer. The Cochrane Center in Oxford, UK, collected all randomized controlled studies using dietary fiber as intervention until October 2001, and used systematic review and meta-analysis to evaluate the protective effect of dietary fiber on reducing the occurrence and recurrence of colorectal adenomas and the occurrence of colon cancer. A total of 5 clinical trials met the analysis criteria, involving 4,349 subjects. The analysis found that the relative risk (RR) of colorectal adenoma between the intervention group and the control group for 2 to 4 years of dietary intervention with added wheat bran or a high-fiber comprehensive diet was 1.04 (95% CI: 0.95-1.13), and the risk difference (RD) was 0.01 (95% CI: 0.02-0.04). The authors concluded that "so far, there is insufficient evidence from randomized controlled clinical trials to support that increasing dietary fiber intake can reduce the occurrence or recurrence of colorectal adenomas in 2 to 4 years. Because the interactions between nutrients in the diet are very complex, the type of diet is more important than the specific ingredients, and dietary intervention is often not effective due to the addition of a single factor. In addition, the occurrence and development of tumors is a long process, and dietary intervention is also a behavioral intervention. The protective effects of dietary fiber and other dietary components need to be verified with more scientific, more rigorous designs and long-term prospective studies. (2) Chemoprevention Chemoprevention is a new concept of tumor control proposed in recent years. It refers to the use of one or more natural or synthetic chemical agents, namely chemoprevention agents (chemoprevention agents). Chemopreventive agent (CPA) can prevent the occurrence of tumors. In a broad sense, dietary intervention is also a form of chemical prevention. Because it is achieved by changing eating habits, it can also be regarded as a behavioral intervention. Chemopreventive agents can prevent the occurrence of tumors and inhibit their development by inhibiting and blocking the formation, absorption and action of carcinogens. According to Vogelstein's colon cancer carcinogenesis model, colon cancer develops from normal mucosa, through a series of molecular biological events, with adenoma as the intermediate stage, and finally malignant transformation. Chemopreventive agents can inhibit or reverse the occurrence of adenoma or inhibit its progression to malignant lesions at different stages (Figure 13). ① Aspirin and other nonsteroidal anti-inflammatory drugs: Aspirin and other nonsteroidal anti-inflammatory drugs (nonsteroidalantinflammatorydrugs , NSAIDs) are the most widely studied chemopreventive agents for colon cancer. Their main mechanism is to block the synthesis of prostaglandins, promote tumor cell apoptosis, and inhibit tumor angiogenesis through irreversible acetylation and competitive inhibition of cyclooxygenase-1 and cyclooxygenase-2 (COX-1 and COX-2). Thun et al. reported in 1991 that a survey of 662,424 people taking aspirin between 1982 and 1989 showed that the risk of death from colon cancer for those who did not take aspirin regularly was 0.77 for men and 0.73 for women compared to those who did not take aspirin regularly. The risk of death from colon cancer for men and women who took aspirin regularly was further reduced to 0.60 and 0.58, respectively. In a two-year follow-up survey of 47,900 medical staff, it was found that those who took aspirin regularly based on a single survey had a lower risk of death from colon cancer than those who did not take aspirin regularly. The relative risk of colorectal cancer is 0.68, and the relative risk of "regular users" determined by more than three surveys is further reduced to 0.35. In the nurse health survey conducted by Giovannucci et al., it was also found that among 89,446 female nurses, those who regularly took aspirin had a risk of colon cancer of 0.62, and those who took it for more than 20 years had a risk further reduced to 0.56. However, the role of aspirin in preventing colon cancer has not been proven by randomized controlled clinical trials. In a trial of 22,071 male medical personnel using aspirin to prevent coronary heart disease, the relationship between aspirin and colon cancer was also analyzed. The data showed that there was no significant difference between the experimental group and the control group in the occurrence of colon cancer, colon polyps or carcinoma in situ. According to analysis, this may be related to low aspirin doses, short continuous use time or insufficient follow-up time. There are few reports on the protective effect of non-aspirin NSAIDs on colon cancer. Recently, a large-sample retrospective survey found that the relative risk of colon cancer in 104,217 people aged 65 and above who took non-aspirin NSAIDs prescribed by Medicaid was 0.61. Of course, its effect should be confirmed by a carefully designed prospective study. ② Folic acid: Folic acid is a micronutrient in the diet and is abundant in vegetables and fruits. Epidemiological studies have found that people with high folic acid intake have a low incidence of colon cancer, while reduced folic acid intake (often seen in heavy drinkers) increases the risk of colon cancer and colorectal adenoma. Studies have shown that a diet containing a lot of folic acid has a certain protective effect on the occurrence of colon cancer (RR = 0.78 for men and RR = 0.91 for women), and the effect of adding folic acid to the diet is more obvious (RR = 0.63 for men and RR = 0.66 for women). In Giovannucci's nurses' health survey, women who took more than 400 μg of folic acid per day had a very significant protective effect against colon cancer (RR=0.25), but this protective effect would only be apparent after 15 years of use, suggesting that folic acid plays a role in the early stages of colon cancer. ③ Calcium: Most case-control and cohort studies in humans have shown that a high calcium diet and the use of calcium supplements are negatively correlated with the occurrence of colon cancer and colorectal adenoma, but only some of the results are statistically significant. The main reason may be the inaccurate estimation of calcium intake or the confounding effect of other dietary factors. In recent years, Baron et al. reported that 930 patients with a history of colorectal adenoma were randomly divided into two groups: taking calcium supplements (3g/d calcium carbonate, containing 1.2g of calcium) or placebo. Colonoscopy was performed one year and four years after the start of the study. The incidence of adenoma in the group taking calcium tablets decreased to a certain extent, which was significantly different from the placebo group (RR=0.85). Moreover, the protective effect of calcium supplements can be observed one year after taking the medicine. ④ Estrogen: In the past 20 years, the mortality rate of colon cancer in American men has been declining, and it is more obvious in women. One explanation is that hormone replacement therapy is widely used in women after menopause. The mechanism of estrogen in preventing colon cancer may be related to reducing the production of secondary bile acid, reducing insulin growth factor-1, or directly acting on the intestinal mucosal epithelium. Calle et al. reported that the mortality rate of colon cancer in women who used hormone replacement therapy was significantly reduced (RR=0.71), and it was more significant in those who used it for more than 11 years (RR=0.54). Similar results were found in the Nurses' Health Study (RR=0.65), but the protective effect of hormones disappeared 5 years after stopping the drug. The results of two meta-analyses published in recent years also showed that hormone replacement therapy can reduce the overall risk of colon cancer by 20%. The above observations suggest that the protective effect of estrogen may occur in the late stage of colon cancer. ⑤ Vitamins and antioxidants: For many years, it has been believed that vitamins and antioxidants in vegetables and fruits can reduce the incidence of colon cancer, but many prospective studies do not support this hypothesis. For example, the Nurses' Health Study and the Physicians' Health Study did not find any protective effect of adding beta-carotene, vitamin A, B, D or E to the diet on colon cancer. In a randomized controlled study, 864 patients with a history of colorectal adenoma were given placebo, beta-carotene, vitamin C and vitamin E, or beta-carotene combined with vitamins C and E. Colonoscopy was performed 1 year and 4 years later, and no difference was found in the occurrence of adenoma among the four groups. (3) Treatment of precancerous lesions It is generally believed that precancerous lesions of colon cancer include adenomatous polyps, ulcerative colitis and Crohn's disease, and adenoma is particularly closely related to colon cancer. Epidemiological, animal experiments, clinical and pathological studies have confirmed that the vast majority of colon cancers are caused by adenoma cancer, especially large, villous and severely atypical adenomas are more likely to become cancerous. According to Morson's study, if colorectal adenomas are not removed, 4% of patients may develop colon cancer within 5 years, and 14% may become cancerous within 10 years. Stryker et al. also proved that the incidence of colon cancer in patients with untreated colorectal adenomas can be as high as 24% within 20 years. Therefore, early detection and timely treatment of colorectal adenomas are ideal ways to prevent and reduce the occurrence of colon cancer. Gilbertsen began to perform sigmoidoscopy (hard endoscope) examinations on asymptomatic people over 45 years old once a year since the 1950s, and removed polyps if found. A total of 18,158 people were examined in 25 years, and only 13 cases of low-position colon cancer occurred among the examined population, all of which were early-stage, a decrease of 85% from the expected 75 to 80 cases. In 1976, Lee analyzed the changing trend of colorectal cancer incidence in the United States over 25 years and found that the incidence of colon cancer increased significantly while that of rectal cancer decreased by 23%. In the 1950s, rectal cancer accounted for 55% of colon cancer, while in the 1970s it was only 30.7%. He believed that the reason for the reduction in rectal cancer was probably the result of the widespread implementation of sigmoidoscopy and the active treatment of low-position adenomas found. Zhejiang Medical University in China conducted a colon cancer survey on people over 30 years old in Haining City from 1977 to 1980. A total of 238,826 15cm colonoscopy examinations were completed in two screenings, and 4,076 low-lying colon polyps were found, of which 1,410 adenomas were surgically removed. By 1998, a total of 6 colonoscopy or 60cm fiber sigmoidoscopy follow-up examinations (after 1988) were performed, and all detected polyps were removed. According to the Haining City Tumor Registration Data, the average incidence and mortality of rectal cancer in the city from 1992 to 1996 decreased by 41% and 29% respectively compared with 1977 to 1981. However, the value of removing precancerous lesions for colon cancer prevention has yet to be confirmed by more rigorous clinical trials. For this purpose, the U.S. NCI funded a multicenter prospective clinical trial (National Polyp Study, NIPS) participated by 7 units including the Memorial Sloan-Kettering Cancer Center. The NPS included 9,112 patients who underwent full colonoscopy between 1980 and 1990. There were 2,632 patients with adenoma who met the research criteria. After the removal of adenoma, 1,418 of them were randomly divided into two groups for follow-up at different examination frequencies. Full colonoscopy and barium enema were performed during the follow-up. The average follow-up time was 5.9 years. During this period, only 5 cases of asymptomatic early colon cancer (polyp canceration) were found, and no invasive colon cancer. Compared with the two reference groups of patients with a history of polyps who did not undergo surgical removal, the incidence of colon cancer in this group of patients decreased by 90% and 88% respectively. Compared with the general population, the incidence of colon cancer in this group also decreased by 76%. This study fully supports the view that colorectal adenomas can develop into colorectal adenocarcinoma, and further proves that the treatment of precancerous lesions can prevent the occurrence of colon cancer. 2. Secondary prevention Screening of high-risk populations for colon cancer in order to find asymptomatic preclinical tumor patients. Achieve early diagnosis and early treatment, improve the survival rate of patients, and reduce the mortality rate of the population. Screening can not only detect early colon cancer, but also detect precancerous lesions of colon cancer, such as adenomatous polyps, so that they can be treated in time to prevent the occurrence of cancer. In this sense, screening is both a secondary prevention measure for colon cancer and an effective primary prevention measure. The natural history of colon cancer is relatively long. It takes multiple molecular biological events such as gene deletion and mutation to develop from precancerous lesions to invasive tumors. It is estimated that it takes 10 to 15 years, which provides an opportunity for screening to detect early lesions. The prognosis of early colon cancer is good. According to the data of the US NCI Disease Surveillance (SEER), among the 59,537 cases of colon cancer from 1978 to 1983, the 5-year survival rate of carcinoma in situ was 94.1%, that of local lesions (Dukes' A) was 84.6%, and that of distant metastasis dropped to 5.7%. Among the 1,385 cases of colon cancer in Shanghai Cancer Hospital, the 5-year survival rates of Dukes A, B, C, and D were 93.9%, 74.0%, 48.3%, and 0.31%, respectively. However, in general clinical cases, the proportion of stage A+B is often only about 40%, while stage C+D is as high as 60%. Armitage reported that in most hospitals in the UK, Dukes' stage A only accounted for 6%. Since early colon cancer is mostly asymptomatic or the symptoms are not obvious, it is now certain that screening can increase the detection rate of early cases, and at the same time, precancerous lesions can be found and treated in time, thereby reducing the occurrence of colon cancer. It can be inferred that colon cancer screening may reduce the mortality rate of the population. From 1973 to 1995, the mortality rate of colon cancer in the United States decreased by 20.5%, and the incidence rate decreased by 7.4%, especially after 1986. The rate of decline accelerated. It is generally believed that this may be related to the widespread implementation of colon cancer screening and the removal of polyps by colonoscopy, and is unlikely to be the result of changes in diet and lifestyle habits. Recently, the NCI, the United States Preventive Services Task Force (USPSTF), and the American Gastroenterological Association evaluated the commonly used methods of colon cancer screening, including: digital rectal examination, fecal occult blood test, sigmoidoscopy, barium enema, and colonoscopy. This is the most authoritative and comprehensive review of the evidence on the effectiveness of colon cancer screening to date. (1) Digital rectal examination Digital rectal examination is simple and easy to perform. It can examine the rectum within 8 cm from the anus. About 30% of colorectal cancers in Chinese people are within this range, but only 10% of colorectal cancers in Europe and the United States can be detected by digital rectal examination. In the colon cancer screening in Haining City, China, the polyp detection rate of sigmoidoscopy (15-18 cm) was 1.7%, while that of digital rectal examination was only 0.17%. In addition, during large-scale examinations, the examiner's fingertips are swollen and they lose their sense of feeling, resulting in a lower detection rate. A case-control study in the United States showed that the ratio of patients who died of distal rectal cancer over 45 years of age from 1971 to 1986 to receive anal fingerprint diagnosis one year before diagnosis was not different between the two groups (OR=0.96). Therefore, anal fingerprint diagnosis has limited effect as a screening method, but is clinically indispensable for the whole physical examination of symptomatic patients. (2) Fecal occult blood test Invisible intestinal bleeding is the most common early symptom of colon cancer and colorectal adenoma. Since Greegor first screened for colon cancer with FOBT in 1967, FOBT has been the most widely used method of colon cancer screening due to its economic, simplicity and safety. The existing methods of occult blood test are mainly chemical methods and immunologic methods. Among chemical methods, guaiacin lester reagent Hemoccult II (SmithKline Diagnostics) is the most widely used and most studied. It uses the peroxidase-like activity of heme to react with guaifenesin in the presence of H2O2 to produce blue color; therefore, animal blood, red meat, some vegetables such as carrots, turnips, cauliflower, certain drugs such as iron, nonsteroidal antipyretic and painkillers, etc., can also produce false positive reactions. It is generally believed that the daily intestinal physiological bleeding of normal people is less than 2ml, while the detection sensitivity of Hemoccult II is 4-6ml/100g of feces, so FOBT positive indicates pathological bleeding. Ransohoff and Lang systematically evaluated FOBT and found that the sensitivity of colon cancer screening for single unhydrated FOBT was 40%, specificity was 96% to 98%, and the sensitivity after hydration increased to 50% to 60%, but the specificity decreased to 90%. Recently, Lieberman et al. reported that the sensitivity of colon cancer screening for hydrated FOBT was 50% (95%CI: 30% to 70%), and the sensitivity to cancer and precancerous lesions (large villous adenocarcinoma with atypical hyperplasia) was 24% (95%CI, 19% to 29%), and the specificity was 94% (95%CI, 93% to 95%). Among people over 50 in Western countries, the FOBT positive rate was 2% under dietary control conditions. Among FOBT positive patients, about 10% were colon cancer and 30% were polyps. However, the false positive rate of chemical FOBT (benzidine method) in normal people surveyed in my country can be as high as 12.10% (23706/206125), which greatly limits its application value. This may be related to the high prevalence of other gastrointestinal bleeding diseases in Chinese people such as gastritis, gastric ulcers, gastric cancer and hemorrhoids. The earliest clinical trial of FOBT screening for colon cancer was hosted by Sloan-Kettering Memorial Cancer Center from 1975 to 1985. 21,756 asymptomatic people over 40 years old participated in the screening test, and randomly divided into the screening group and the control group. Among the detected colon cancers, 65% of the screening group were Dukes' A and B stages, while only 33% of the control group; the 10-year survival rate of the screening group was significantly higher than that of the control group (the sensitivity of P10mm adenoma was 47.4% (9/19), the specificity of the detection of normal people over 40 years old was 97.9% (88/98), and the specificity of normal people under 30 years old was 97.8% (92/94). The study proved that immunologic FOBT, including InSureTM, does not have myoglobin. , animal hemoglobin reaction, is not disturbed by diet and drugs, and is negative for feces with upper gastrointestinal bleeding. Recently, the American Cancer Society (ACS) Colon Cancer Advisory Group evaluated the existing evidence, believing that immunologic FOBT can increase the specificity of screening compared with chemical FOBT. The following instructions were added to the 2003 ACS colon cancer screening guide: "In terms of detecting fecal occult blood, immunologic occult blood test is easy to accept for patients, and its sensitivity and specificity are better than or at least the same as the hemologous method." (4) Gilbertsen began screening colon cancer and polyps with sigmologous colonoscopy as early as the early 1950s, and 18,158 people were regularly tested for sigmologous (25cm hard lens) and found after 25 years of follow-up Compared with the national average, the incidence of sigmoid colon and rectal cancer in the screening group has significantly decreased. Due to the difficulty of inserting a rigid giocoloscope, the patient acceptance rate is low. Since the invention of optical fiber giocoloscope in 1969 and the introduction of 60cm fiber giocoloscope in 1976, 25cm hard lens has been replaced by 60cm fiber colonoscopy. More than 80% of family physicians in the United States have equipped and used 60cm colonoscopy. The Kaisei Health Checkup in the United States (Kaiser Permanence Multiphasic Health Checkup, MHC) randomly divided 10,713 people aged 35 to 54 into trial and control groups. Among the 5,156 people who were screened, 20 cases of colon cancer were detected, and their : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : According to my country's national conditions, 60cm fiber colonoscopy cannot be used as a primary screening method, but it is still worthy of vigorous promotion as a simple and feasible and relatively reliable re-screening or diagnostic measure. At present, at least two case-control studies have shown that screening with sigmoidoscopy can reduce the mortality rate of colon cancer. Selby's study was sigmoidoscopy, while Newcomb's study was mainly fibrous gicoscopy. Both studies showed that those who had done more than one gicoscopy had a 70% to 90% lower risk of dying from distal colon and rectal cancer than those who had never had a microscopy. According to This-Evensen and others, 799 subjects were selected from the general population in Norway in 1983 and randomly divided into B colonoscopy screening group and control group. 81% of the screening groups underwent B colonoscopy. If polyps were found, then a whole colonoscopy was performed. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : Winawer and others used the national polyp study data, and used the results of whole colonoscopy as the gold standard to evaluate DCBE. They found that 1 cm polyps (including 2 cancerous polyps) was 48%, while DCBE specificity was 85%. Although DCBE is low in sensitivity, it can be checked for the whole colon, with a low complication rate and is widely accepted by medical staff and patients, so it can still be used as one of the methods of colon cancer screening. (7) Other technologies In response to the new technologies for detecting colon cancer and adenomatous polyps in recent years, the ACS Colorectal Cancer Advisory Group (ACSColectal Cancer Advisory Group) held a seminar in April 2002 to evaluate the effects of CT colorectal imaging, immunosolution fecal occult blood test, fecal molecular marking and capsule video endoscopy in colon cancer screening and obtained consensus. CT Colonography, also known as virtual colonoscopy, first appeared in 1994. It uses spiral CT to quickly multiple scans to perform two-dimensional or three-dimensional imaging of the internal structure of the colon to simulate the results of the colonoscopy, but avoids the invasive operation of the colonoscopy. According to the results of multiple US centers, the sensitivity of CT CT colorectal imaging of polyps >1cm is close to 90%, and