Sigmoid colon cancer

Introduction to sigmoid colon cancer Sigmoid colon cancer is a type of colon cancer. Early symptoms can be manifested as: abdominal pain, indigestion, bloating, and abnormal bowel movements may occur later. The site of the disease is located at a segment of the colon between the descending colon and the rectum. basic knowledge Sickness ratio: 0.05% Susceptible people: no specific population Mode of infection: non-infectious Complications: anemia

Cause of sigmoid colon cancer

1. Age of onset, most patients develop after 50 years of age.

2, family history: If a person's first-degree relatives, such as parents, have had colorectal cancer, he is 8 times more likely to suffer from this disease in his lifetime than the general population, about a quarter of new patients Have a family history of colorectal cancer.

3, history of colon disease: some colon diseases such as Crohn's disease or ulcerative colitis may increase the incidence 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. They are called polyps. Among them, villus-like adenomatous polyps are more likely to develop into cancer, and the chance of cacao becomes about 25%. Tubular adenocarcinoma The polyposis rate is 1-5%.

5, genetic characteristics: some familial tumor syndrome, such as hereditary non-polyposis colon cancer, can significantly increase the incidence of colorectal cancer, and the onset time is younger.

Sigmoid colon cancer prevention

Colon cancer is the third leading cause of death in the world. Although the treatment of colon cancer has made great progress, the 5-year survival rate of advanced colon cancer has not changed much. Therefore, the significance of colon cancer prevention is becoming more and more important.

According to the multi-stage theory of the cancer process. The occurrence of colon cancer also undergoes three stages of initiation, promotion, and progression. In morphology, it is characterized by normal mucosa hyperplasia adenoma formation adenoma carcinogenesis infiltration and metastasis. If the cancer of familial adenomatous polyposis becomes 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 interventions at different stages of the natural history of colon cancer, China has developed the following prevention strategies.

1, primary prevention

Eliminate or reduce the exposure of the large intestinal mucosa to carcinogens before tumor formation, inhibit or block the carcinogenesis of epithelial cells, thereby preventing tumorigenesis. These include dietary interventions, chemoprevention, and treatment of precancerous lesions.

(1) Dietary intervention

British scholar Burkitt has long pointed out that colon cancer is a "modern disease" associated with modern lifestyles and diet types. A large number of epidemiological studies, especially immigration epidemiological studies, show that colon cancer has excessive onset and energy intake, obesity, excessive intake of saturated fatty acids, decreased physical activity, dietary fiber and micronutrients (vitamins A, E, C, trace element selenium and calcium) are associated with insufficient intake.

Dietary fiber is the most studied in terms of dietary intervention. As early as the 1960s and 1970s, Burkitt found that colon cancer was very rare among African blacks, and the African aborigines' diet contained a lot of dietary fiber, so he proposed that the high-fiber diet is a hypothesis for colon cancer protection factor. Subsequent studies have shown that dietary fiber can dilute or absorb carcinogens in the feces, speeding up the passage of food residues in the intestines, thereby reducing the exposure of intestinal mucosa to carcinogens in food. At the same time, dietary fiber can also protect colon cancer by changing the metabolism of bile acid, lowering the pH of the colon and increasing the production of short-chain fatty acids.

Early observational epidemiological studies and case-control studies have shown that dietary fiber has a protective effect on colon cancer with increasing 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 these studies supported a negative correlation between dietary fiber intake and colon cancer incidence; The intake of C and beta carotene has only a small negative correlation with the onset of colon cancer.

In the prospective clinical intervention trials, such as the occurrence of colon cancer as an "end-point", long-term follow-up is required to reach a definitive conclusion, so some people advocate the use of precancerous lesions - adenoma (or recurrence) As an indicator of the risk of colon cancer, in recent years, some "intermediate markers" have been advocated to evaluate the effects of interventions, in order to greatly shorten the time required for intervention trials.

The most commonly used meta-term index is the rectal mucosal crypt sputum-labeled thymidine (HTdR) incorporation index (LI), which reflects the proliferation of cells. Studies have confirmed that LI is associated with colon cancer risk and has been widely used in diets. Evaluation of the intervention trial. In recent years, immunohistochemical assays have been established to detect the incorporation of brominated deoxyuridine (Br-UdR) and proliferating cell nuclear antigen (PCNA). These assays do not require radionuclides to reflect cell proliferation. Other intermediate indicators for evaluation included microscopic examination of abnormal crypts and microadenomas, as well as protein kinase C (PKC) and ornithine decarboxylase (ODC) activities.

(2) Chemoprevention

Chemoprevention is a new concept of tumor control proposed in recent years. It refers to the prevention of tumorigenesis by one or more natural or synthetic chemical agents, chemopreventive agents (CPA). In a broad sense, dietary intervention is also a kind of chemoprevention, which can be seen as a behavioral intervention because it is achieved by changing eating habits. Chemopreventive agents prevent the onset of tumors and inhibit their development by inhibiting and blocking the formation, absorption and action of carcinogens.

According to Vogelstein's colon cancer model, colon cancer is completed from a normal mucosa, through a series of molecular biological events, with an adenoma as an intermediate stage, and finally malignant, and chemopreventive agents can repress or reverse the occurrence of adenoma at different stages. Or inhibit its progression to malignant lesions (Figure 13).

1 Aspirin and other non-steroidal anti-inflammatory drugs: Aspirin and other nonsteroidal ant inflammatory drugs (NSAIDs) are the most widely studied colon cancer chemopreventive agents, the main mechanism is through irreversible acetylation and competitive inhibition ring Oxidase-1 and cyclooxygenase-2 (COX-1 and COX-2) block the synthesis of prostaglandins, promote tumor cell apoptosis, and inhibit tumor angiogenesis. Thun et al. reported in 1991 that 662,424 people were taking aspirin between 1982 and 1989. Infrequent use of those who died of colon cancer was 0.77 for men and 0.73 for women. The risk of male and female dying from colon cancer was further reduced to 0.60 and 0.58, respectively. In a 2-year follow-up survey of 47,900 medical staff, the relative risk of colon cancer was 0.68, as determined by a single survey, and the regular use determined by more than 3 surveys. The relative risk is further reduced to 0.35. In the nurses' health survey of Giovannucci et al., the risk of colon cancer in 89,46 female nurses who regularly took aspirin was 0.62, and the risk of taking 20 years or more was further reduced to 0.56.

However, the role of aspirin in preventing colon cancer has not been demonstrated in randomized controlled clinical trials. In a trial of 22071 male medical staff using aspirin to prevent coronary heart disease, the relationship between aspirin and colon cancer was also analyzed. The data showed that the experimental group and the control group had no evidence of colon cancer, colon polyps or carcinoma in situ. Significant differences, according to analysis, may be related to low doses of aspirin, short duration of administration or insufficient follow-up time.

There are few reports on the protective effect of non-aspirin NSAIDs on colon cancer. A recent large-scale retrospective found that 104,217 elderly people over the age of 65 were taking prescriptions for non-aspirin NSAIDs from Medicaid. The relative risk of colon cancer is 0.61, and of course, its role should be confirmed by well-designed prospective studies.

2 folic acid: folic acid is a micronutrient in the diet, rich in vegetables and fruits, epidemiological studies found that people with high folic acid intake have a low incidence of colon cancer, while decreased folic acid intake (often seen in large drinkers) increases Risk of colon cancer and colorectal adenoma. Studies have shown that diets containing large amounts of folic acid have a protective effect on colon cancer (male RR = 0.78, female RR = 0.91), while the effect of adding folic acid to the diet is more pronounced (male RR = 0.63, female RR = 0.66). ). In Giovannucci's nurse health survey, women's daily intake of more than 400g of folic acid has a significant protective effect on colon cancer (RR=0.25), but the protective effect will not appear until 15 years later, suggesting that folic acid is in the early stage of colon cancer. Play a role.

3 Calcium: Case-control and cohort studies in the human body Most showed that the application of high-calcium diet and calcium additive was negatively correlated with the occurrence of colon cancer and colorectal adenoma, but only some of the results were statistically significant. The main reason may be that the calcium intake is not accurately estimated or is related to other dietary factors. In recent years, Baron et al reported that 930 patients with a history of colorectal adenoma were randomized to receive calcium supplements (3 g/d calcium carbonate, 1.2 g calcium) or placebo. Colonoscopy was performed at 1 and 4 years after the start of the study. The incidence of adenoma in the calcium group was decreased, which was significantly different from the placebo group (RR=0.85). Moreover, the protective effect of calcium additive was 1 after taking the drug. It can be observed in years.

4 Estrogen: In the past 20 years, the mortality rate of colon cancer in males in the United States has been decreasing, while women are more obvious. One explanation is that women use hormone replacement therapy extensively after menopause. The mechanism by which estrogen prevents colon cancer may be related to reducing secondary bile acid production, decreasing insulin growth factor-1, or directly acting on intestinal mucosal epithelium.

Calle et al reported that colon cancer mortality was significantly lower in women who received hormone replacement therapy (RR = 0.71), and more significant in patients who continued to use for more than 11 years (RR = 0.54). Similar results were found in the nurses' health study (RR = 0.65), but the protective effects of hormones disappeared 5 years after discontinuation. The results of two meta-analyses published in recent years have also shown 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: Vitamins and antioxidants in vegetables and fruits have been thought to reduce the incidence of colon cancer for many years, but many prospective studies do not support this hypothesis. For example, nurse health research, doctor health research, etc. have not found the addition of beta carotene to the diet, vitamin A, B, D or E for colon cancer.

In a randomized controlled trial, 864 patients with a history of colorectal adenoma were given a placebo, beta carotene, vitamin C and vitamin E, and beta carotene and vitamins C and E. Colonoscopy was performed 1 year and 4 years later, and no difference was found in the 4 groups of adenomas.

(3) Treatment of precancerous lesions

Precancerous lesions of colon cancer are generally considered to include adenomatous polyps, ulcerative colitis, and Crohn's disease, and adenomas are particularly closely related to colon cancer. Epidemiology, animal experiments, and clinical and pathological studies have confirmed that the vast majority of colon cancers are cancerous from adenomas, especially large, villous, and adenomas with severe atypical hyperplasia. According to Morson's study, if the colorectal adenoma is not removed, colon cancer can occur in 4% of patients within 5 years, and 14% can be cancerous within 10 years. Stryker et al also demonstrated that untreated colorectal adenoma patients can have a colon cancer rate of up to 24% within 20 years. Therefore, early detection and timely treatment of colorectal adenoma is an ideal way to prevent and reduce the occurrence of colon cancer. Gilbertsen began to perform sigmoidoscopy (hard-slice) examinations every year for asymptomatic people over 45 years old in the 1950s. He found that polyps were removed. A total of 18,158 people were examined in 25 years, and only 13 cases of low colon cancer occurred in the tested population. And both are early, which is 85% lower than the expected 75-80 cases. In 1976, Lee analyzed the trend of colorectal cancer in the United States for 25 years. The incidence of colon cancer increased significantly while rectal cancer decreased by 23%. In the 1950s, rectal cancer accounted for 55% of colon cancer, but in the 1970s it was only 30.7%. It is believed that the cause of the reduction in rectal cancer is likely to be the result of extensive sigmoidoscopy and active treatment of low adenomas found.

However, the value of removing precancerous lesions for colon cancer prevention remains to be confirmed by more rigorous clinical trials. To this end, the US NCI funded a multi-center prospective clinical trial (National Polyp Study, NlPS) involving seven units including the Sloan-Kettering Memorial Cancer Center. In the NPS, 9112 patients who underwent total colonoscopy between 1980 and 1990, 2632 patients with adenomas who met the study conditions, and 1418 patients with adenoma were randomly divided into 2 groups and followed up according to different examination frequency. At the time of total colonoscopy and barium enema, the average follow-up time was 5.9 years, during which only 5 asymptomatic early colon cancers (polyposis) were found, but no invasive colon cancer. The incidence of colon cancer in this group was reduced by 90% and 88%, respectively, compared with the two reference groups in patients with polyp history without surgical removal. The incidence of colon cancer in this group also decreased by 76% compared with the general population. This study fully supports the idea that colorectal adenoma can develop into colorectal adenocarcinoma, and it proves that the treatment of precancerous lesions can prevent the occurrence of colon cancer.

2, secondary prevention

Screening for high-risk populations of colon cancer to identify asymptomatic preclinical tumor patients. Early diagnosis and early treatment can improve the survival rate of patients and reduce the mortality rate of the population. Because screening can not only find early colon cancer, but also the precancerous lesions of colon cancer - adenomatous polyps, so that it can be treated in time to prevent 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 long. From the development of precancerous lesions to invasive tumors, it is necessary to undergo molecular biological events such as multiple gene deletions and mutations. It is estimated that it takes 10 to 15 years, which provides a screening for early lesions. opportunity. Early colon cancer has a good prognosis. According to the US NCI disease surveillance (SEER) data, the 5-year survival rate of carcinoma in situ was 94.1% and the local lesion (Dukes'A) was 84.6% in 59,537 colon cancers from 1978 to 1983. When there is a distant transfer, it drops to 5.7%.

(1) Anal diagnosis

Anal examination is simple and easy, you can check the rectum within 8cm from the anus. About 30% of colorectal cancer in the country is within this range, but only 10% of colorectal cancer in Europe and America can be diagnosed by anal examination. The detection rate of polyps in the sigmoid colonoscopy (15-18 cm) of colon cancer in Haining City in China was 1.7%, while the anus was only 0.17%. In addition, when the large-scale examination, the examiner's swelling and sensation of the fingertips failed, resulting in a decrease in the detection rate. A case-control study in the United States showed that patients who died of distal rectal cancer between the ages of 45 and 1971 between 1971 and 1986 had no difference in the rate of anal examinations 1 year before diagnosis compared with the control group (OR= 0.96). Therefore, anal digital examination has a limited effect as a screening method, but it is an essential part of a full physical examination for symptomatic patients.

(2) fecal occult blood test

Intestinal invasive bleeding is the most common early symptom of colon cancer and colorectal adenoma. Since Greegor first screened colon cancer with FOBT in 1967, FOBT has been the most widely used colon cancer screen because of its economy, simplicity and safety. The methods of detection, the existing methods of occult blood test are mainly chemical methods and immunological methods.

In the chemical method, Hemoccult II (Smith Kline Diagnostics) is the most widely used and most studied. It uses the peroxidase-like activity of heme to react with guaiac in the presence of H2O2 to produce blue color; therefore, animal blood, red meat and some vegetables such as carrots, turnips, broccoli and certain drugs such as iron Non-steroidal antipyretic and analgesic drugs can also produce false positive reactions. It is generally believed that the normal human intestinal gastrointestinal bleeding volume is less than 2ml per day, while the detection sensitivity of Hemoccult II is 4-6ml/100g stool, so FOBT positive indicates pathological bleeding. Ransohoff and Lang systematically evaluated FOBT: the sensitivity of a single unhydrated FOBT screening colon cancer was 40%, the specificity was 96% to 98%, and the sensitivity after hydration increased to 50% to 60%, but The specificity has dropped to 90%. Recently, Lieberman et al reported that hydration FOBT screening for colon cancer sensitivity is 50% (95% CI: 30% to 70%), for cancer and precancerous lesions (large villous with atypical hyperplasia) The adenocarcinoma has a sensitivity of 24% (95% CI, 19% to 29%) and a specificity of 94% (95% CI, 93% to 95%). In the western countries, the FOBT positive rate was 2% under controlled diet conditions, and among FOBT positive patients, about 10% were colon cancer and 30% were polyps. However, the false positive rate of the chemical method FOBT (benzidine method) in the normal population of China's census can be as high as 12.10% (23706/206125), which greatly limits its application value, which may be related to other gastrointestinal bleeding diseases such as gastritis. Gastric ulcer, gastric cancer and high prevalence of sputum are related.

The earliest clinical trial of FOBT screening for colon cancer was hosted by the Sloan-Kettering Memorial Cancer Center from 1975 to 1985. 21,756 asymptomatic individuals over 40 years of age were screened, randomized to the screening group and the control group, in the colon Among the cancers, 65% of the screening group were Dukes'A and B, while the control group was only 33%; the 10-year survival rate of the screening group was significantly higher than that of the control group (P<0.001), and the colon of the screening group was followed up for 10 years. The cancer mortality rate was 43% lower than that of the control group (P=0.053). The study showed an increase in the proportion of early cancer, prolonged survival and decreased colon cancer death. The effect of FOBT on screening for colon cancer can reduce colon cancer mortality, which has been demonstrated by at least three well-designed large-scale randomized controlled clinical trials (Table 6), which is Class I evidence, so the USPSTF prioritizes it as A. Class recommendations (ie strongly recommended) are used for crowd screening.

(3) Immunology

FOBT was developed in the late 1970s. By using the specific immune response of hemoglobin and corresponding antibodies, it avoids the disadvantages of chemical methods to limit diet and improves the specificity and sensitivity of screening. In 1987, Zhejiang Medical University successfully developed the reverse indirect hemagglutination (RPHA-FOBT) kit. In Haining City and Jiashan County, Zhejiang Province, a group of 3034 high-risk populations with a history of rectal polyps were screened for RPHA FOBT. 11 cases of colorectal malignant tumor, 465 cases of polyps (195 cases of adenoma), with 60cm fiber enteroscopy as the reference standard, proved that the sensitivity of RPHA-FOBT screening for colon cancer was 63.6%, specificity was 81.9%, Youden The index is 0.46, which is superior to the chemical method. The study also showed that the sensitivity of RPHA-FOBT screening polyps was only 22.1%, but it was about 40% positive for villous and tubular villous adenomas with a high malignant tendency. On this basis, Zheng Shu et al. used a sequential method for colon cancer screening in 75,813 people over the age of 30 in Jiashan County, a high incidence area for colon cancer. The total positive rate of RPHA-FOBT was 4.2%, and 21 cases of colon were screened. Dukes' A and B in cancer accounted for 71.4%.

A variety of immunological FOBT reagents are available in the United States, such as Hemeselect, InSure, and FlexsureOBT, which use monoclonal or polyclonal antibodies against human hemoglobin to detect fecal occult blood. One of the high-risk groups of 240 colon cancers with InSure TM reagent showed that InSureTM had a sensitivity of 87% (20/23) for screening for colon cancer and 47.4% for adenomas >10 mm. (9/19), the specificity of detection in a group of normal people over 40 years old was 97.9% (88/98), and the specificity of the normal population under 30 years old was 97.8% (92/94). Studies have shown that the immunological method FOBT including InSureTM does not react with myoglobin, animal hemoglobin, is not interfered by diet and drugs, and is negative for feces of upper gastrointestinal bleeding. Recently, the American Cancer Society (ACS) Colon Cancer Advisory Group evaluated the available evidence that immunological FOBT can increase the specificity of screening compared to chemical FOBT, adding the following in the 2003 ACS Colon Cancer Screening Guidelines. Note: "In the detection of fecal occult blood, the immunological occult blood test is easy for patients to accept, its sensitivity and specificity is better than or at least the same.

(4) sigmoidoscopy

Gilbertsen began to screen colon cancer and polyps with sigmoidoscopy in the early 1950s, and sigmoidoscopy (25cm hard) was performed on 18,158 people. After 25 years of follow-up, the screening group was compared with the national average. The incidence of sigmoid and rectal cancer is significantly reduced. Due to the difficulty in inserting the rigid colonoscopy, the patient acceptance rate is low. Since the invention of the optical fiber colonoscopy in 1969, the 60cm fiberoptic colonoscopy was introduced into the clinic in 1976. Now the 25cm hard lens has been replaced by the 60cm fiber enteroscopy. More than 80% of family physicians have equipped and used 60cm colonoscopy.

The Kaiser Permanence Multiphasic Health Checkup (MHC) in the United States randomly divided 10,713 people aged 35 to 54 into trials and controls. Among the 5156 people who were screened, 20 cases of colon cancer were detected, and Dukes' A stage accounted for 60%. After 16 years of follow-up, the 5-year survival rate was 90%, and the 10-year survival rate was 80%. The control group Dukes 'A phase is only 48%, and the 10-year survival rate is also 48%. The number of colon cancer deaths in the experimental group was significantly smaller than that in the control group (12 and 29, respectively). However, further analysis found that, if only the colon cancer mortality rate was within the range that can be achieved by colonoscopy, the difference between the experimental group and the control group was not statistically significant.

Lieberman et al found that 70% to 80% of patients with distal colonic polyps in the fiberoptic colonoscopy also had new organisms in the proximal colon. A randomized controlled trial found that in patients with polyps detected by colonoscopy, the incidence of colon cancer was reduced by 80% after a complete colonoscopy and removal of the adenomas found. Therefore, 60cm fiber enteroscopy for screening can not only remove precancerous lesions within the reach of the endoscope, and can be used as an indication for full colonoscopy, which can reduce the incidence of all colon cancer. Experts believe that if colonoscopy is found to have polyps, the indications for further colonoscopy should be as follows: patients over 65 years old; villi or 1 cm or multiple adenomas; family history of colon cancer.

According to the statistics of 3147 colon cancers in China, 82% occur below the splenic spleen, that is, the 60cm colonoscopy is accessible. Therefore, its application value seems to be larger than that of Western countries. The Cancer Research Institute of Zhejiang Medical University used 60cm fiber enteroscopy as a rescreening method for sequential screening of colon cancer. 60cm colonoscopy was performed on 36.2 high-risk groups, and 21 cases of colon cancer and 331 polyps were found. In another group of 3034 high-risk subjects, 11 cases of colorectal malignant tumors and 563 cases of polyps were detected by 60cm colonoscopy. Before the 60cm colonoscopy, mannitol powder and plenty of drinking water were used for intestinal preparation. The intestinal cleanliness was satisfactory or basically satisfactory in 95%, and all of the more than 6,000 colonoscopy examinations did not have a perforation. According to China's national conditions, 60cm fiber enteroscopy can not be used as a primary screening method, but as a simple, feasible and relatively reliable rescreening or diagnostic measures is still worth promoting.

At least two case-control studies have shown that sigmoidoscopy can reduce the mortality of colon cancer. In Selby's study, sigmoid colonoscopy is used, while Newcomb's study is mainly fiberoptic colonoscopy. Both studies showed that those who had had more than one colonoscopy had a 70% to 90% reduction in the risk of dying from distal colon and rectal cancer than those who had never had a microscopy.

According to Thiis-Evensen et al., 799 subjects were randomly selected from the Norwegian general population in 1983 and randomly divided into the colonoscopy group and the control group. 81% of the screening group received a colonoscopy, such as polyps. mirror. 13 years later (1996), 451 (71%) of the 2 groups underwent total colonoscopy and found no difference in the incidence of polyps between the screening group and the control group, but the screening group had high-risk polyps (1 cm, with atypical The incidence of hyperplasia was lower than that of the control group (RR=0.6, 95% CI: 0.3-1.0, P=0.07), and another 2 cases of colon cancer occurred in the registered screening group and 10 cases in the control group (RR=0.2, 95% CI: 0.03 to 0.95). However, because the overall mortality rate of the screening group is greater than that of the control group (mainly due to cardiovascular disease death), it is difficult to conclude that the colonoscopy screening is conducive to reducing the mortality rate of colon cancer. Currently, there are two randomized controlled trials of sigmoidoscopy screening for colon cancer in the United Kingdom and the United States. Despite the lack of reliable evidence for the efficacy of sigmoidoscopy in the screening of colon cancer, ACS and USPSTF still recommend 60 cm fiberoscopy as one of the primary means of colon cancer screening.

(5) total colonoscopy

Colon cancer screening with a full colonoscopy alone has reduced the incidence and mortality of colon cancer. There are no clinical trials, but full colonoscopy is often combined with other screening methods, such as FOBT or sigmoidoscopy, to reduce the incidence of colon cancer. The effect of death is clear. Lieberman and Imperiale have shown that half of patients with progressive neoplasms (1 cm in diameter, villous adenomas and carcinomas with atypical hyperplasia) have no distal colon and rectal polyps. The need for a full colonoscopy as a screening tool. However, colonoscopy is expensive, preparation is complicated, patient acceptance is poor, and there is a certain complication rate (several complication rate is about 0.3% of perforation bleeding, and the mortality rate is about 1/20000). Therefore, it is reasonable to use colonoscopy alone for screening. Sex is subject to further verification.

(6) Gastric double contrast enema

Although the ACS recommendation has used a double contrast enema (DCBE) as a screening tool for colon cancer every 5 years, no studies have shown that DCBE is effective in reducing the incidence and mortality of colon cancer. Winawer et al. used national polyp study data to evaluate the results of total colonoscopy as a gold standard and found that <0 5cm="" dcbe="" 32="" 0="" 6="" 1cm ="" 53="">1cm of polyps (including 2 cases of cancerous polyps) is 48%, while the specificity of DCBE is 85%. Although the sensitivity of DCBE is low, it can be examined in the whole colon, and the complication rate is low. It is widely accepted by medical staff and patients, so it can still be used as one of the screening methods for colon cancer.

3, three levels of prevention

Active treatment of patients with clinical cancer to improve the quality of life of patients and prolong survival.

Sigmoid colon cancer complications Complications anemia

When a tumor develops to a certain stage, especially when it has already caused obstruction, it will trigger a series of symptoms. These include: weakness, fatigue, anemia, unexplained weight loss, persistent abdominal pain, melena or bloody stools, changes in bowel habits, etc.

Sigmoid colon cancer symptoms common symptoms bloating indigestion abdominal pain feces pus and blood low heat fatigue weight loss constipation

1, the earliest can have bloating, discomfort, dyspepsia-like sigmoid cancer symptoms, and then changes in bowel habits, such as increased stools, diarrhea or constipation, anterior abdominal pain. You can have mucus or mucopurux bloody stools later.

2, symptoms of poisoning: due to tumor ulceration blood loss and toxin absorption, often lead to anemia, hypothermia, fatigue, weight loss, edema and other symptoms of sigmoid colon cancer, especially anemia, weight loss.

3, intestinal obstruction sigmoid colon cancer symptoms: incomplete or complete low intestinal obstruction symptoms, such as abdominal distension, abdominal pain, constipation or closed. Physical examination showed abdominal augmentation, intestinal type, partial tenderness, and a strong bowel sound.

4, the symptoms of sigmoid colon cancer abdominal mass: for the tumor or with the omentum, surrounding tissue infiltration and adhesion of the mass, hard, irregular body, and some can have a certain degree of activity with the intestine, tumor invasion in the late stage More often, the mass can be fixed.

Examination of sigmoid colon cancer

1, fecal occult blood (FOBT) test

It is one of the main means of early detection of colon cancer. In 1967, Greegor first used FOBT as a colon cancer test in asymptomatic people. It is still a practical screening method. FOBT has chemical and immunological methods, and chemical methods include benzidine. Test and guaiacol test, but the specificity is not ideal. The immunoassay includes immunosingle expansion (SRID), latex agglutination (LA), convective immunoelectrophoresis (CIE), immunoenzymatic labeling (ELISA) and reverse Indirect hemagglutination (RPHA), etc., in which RPHA is more suitable for large-scale screening, RPHA sensitivity is 63.6%, lower than 72.7% of the benzidine method, and specificity RPHA is 81.9%, higher than the benzidine method. 61.7%, RPHA as a primary screening can significantly reduce the amount of rescreening population, and does not have to control the diet, easy to be accepted by the census population.

2, cytological diagnosis

Colon cancer exfoliative cytology examination methods include: rectal rinsing, swallowing under direct vision of the colonoscopy, airbag wiping in the wire mesh, and smear method at the site of the lesion, but by the colonoscopy, the brushing of the eyesight or the marking of the lesion site The tablets are more practical. If the malignant cells are found to have diagnostic significance, if they are suspected malignant or slightly enlarged, the nuclear heterogeneous cells with increased chromatin are not enough for final diagnosis, but the prompt should be reviewed or biopsy to confirm the diagnosis, although Exfoliated cells find malignant cells, but the treatment plan should still be based on histopathological diagnosis.

3, histopathological examination

The pathological examination of living tissue specimens is the necessary basis for the development of treatment plans.

(1) Polypoid mass: If the tumor is small, the tumor should be cut and taken for examination, and the pedicle should be included. If there is no obvious tumor pedicle, the tumor base mucosa should be cut and sent for inspection at the same time.

(2) When performing biopsy on a large tumor, care should be taken to avoid necrotic tissue on the surface of the tumor. If possible, the tissue at the junction of the base of the tumor and the normal mucosa should be clamped as much as possible, especially if there is a suspected gland. When the tumor becomes cancerous, it is advisable to take more materials.

(3) ulcer-type lesions should clamp the tissue at the edge of the ulcer, and it is not appropriate to take the degeneration of the ulcer surface and necrotic tissue.

Small pieces of living tissue, in the production process, should pay attention to the embedding direction of the mucosa to ensure that the longitudinal section of the gland tube can be observed in the section.

4. Determination of serum carcinoembryonic antigen (CEA)

Originally, in 1965, Gold extracted r-cell membrane glycoprotein from human colon cancer and pancreatic cancer tissues, and found that it is also present in endoderm-derived digestive tract adenocarcinoma and embryonic liver, intestinal and pancreatic tissues of 2 to 6 months. Named CEA, and considered to be a specific measure of colon cancer, it has also been confirmed by subsequent work, CEA content in colorectal cancer tissue is clearly higher than normal tissue, showing its basis for diagnosis, but it has been widely used and further analysis Found in gastric cancer (49% to 60%), lung cancer (52% to 77%), breast cancer (30% to 50%), pancreas (64%), thyroid (60%) and bladder and other tumors also have CEA, so CEA is a malignant tumor-associated antigen, with the highest proportion of colon cancer positive, especially in liver metastasis. It has been reported that in 20 cases of colorectal cancer, the CEA level of portal vein and peripheral vein is compared, and the portal vein is significantly higher. The level of CEA in the peripheral blood indicates that the liver has a role in clearing CEA, but the mechanism remains unclear. In recent years, CEA has been widely used in clinical practice, and its clinical significance is summarized as two aspects:

1 Predicted prognosis: preoperative CEA can predict prognosis, CEA increased recurrence rate, prognosis is worse than normal CEA value, preoperative increase is 50%, CEA is 25%, CEA is normal The value standard, according to the sensitivity, specificity and predicted value of different standards, the correct index with >5g/L is the highest (0.43), which is more suitable than other levels, so the enzyme standard method is 5g/L. It is more appropriate for the normal value standard.

2 postoperative follow-up prediction of recurrence or metastasis: preoperative CEA increased, radical surgery should return to normal within 6 weeks or 1 to 4 months, still have high residuals may remain, it is believed that 10 weeks before the symptoms of recurrence 13 months, CEA has increased, so after the radical surgery, the CEA value should be closely examined and followed up. If necessary, the second surgical exploration is recommended. Moertal et al (1993) reported 417 cases of recurrence, serum CEA determination 59% increased, while 16A increased in 600 cases without recurrence, showing false positives, CEA is more sensitive to liver and retroperitoneal metastasis, but relatively insensitive to lymph node and lung metastasis, the authors counted 115 cases of CEA increased In laparotomy, 47 patients had recurrence (40.1%). Martin reported that 60 patients who underwent reoperation according to CEA, 93.3% confirmed recurrence, 95% of patients with liver metastasis had elevated CEA, and generally had metastasis or recurrence of 17% to 25%. CEA levels are normal, CEA-led second laparotomy is currently the best way to improve the survival rate of recurrent colorectal cancer.

5, genetic testing

With the research of molecular genetics of tumors, the development and application of in vitro gene amplification technology polymerase chain reaction (PCR) has provided a possibility for tumor gene diagnosis. Currently, there are polymerase chain reaction-restricted fragment lengths. The polymorphic analysis (PCR-RFLP) method can detect single-molecule DNA or a sample containing only one target DNA molecule per 100,000 cells. The following two aspects have been studied and applied in colon cancer.

(1) Determination of the mutation rate of Ki-ras gene in colorectal cancer and paracancerous tissues: it is helpful to understand the degree of malignancy of the tumor and provide participation for predicting the prognosis. There are many human tumors in the ras gene, which is a potential tumor marker, a single Point mutation can turn ras gene into oncogene, dry moon wave and other 11 cases (31.4%) with mutation of 12th codon in 35 cases of colorectal cancer in China, and 1 case (2.9%) of 61 mutations. In 1 case, only the codon mutation of the paracancerous tissue was found, but the 13th codon GlyAsD mutation which is more common in colon cancer was not found (Table 4). This method can be further studied and popularized to identify small pieces of tissue. Cancer is helpful.

(2) Detection of mutant Ki-ras gene in feces: Dry moon wave, etc. Separation of macromolecular DNA from feces for PCR amplification of exon 1 of Ki-ras gene, and detection of 12-position codon of the gene by RFLP method No mutations, 6 cases of colorectal cancer patients with Ki-ras mutations (33.3%), 4 of which also found that the cancer tissue also has corresponding mutations, Volgelstein et al. 24 cases of suspected colon cancer stool examination, 9 There are ras genes in the case, and 8 cases have mutations. The detection method can be used for highly suspicious and general methods to detect the population, which has practical application prospects for early detection of colorectal cancer.

6, fiber colonoscopy

The application of fiberoptic colonoscopy is an important advance in the diagnosis of colon tumors, which also improves the rate of early diagnosis. The application of short fiber sigmoidoscopy gradually replaces the examination of 30cm hard sigmoidoscopy, and the fiber is seen from two kinds of mirror effects. Compared with hard mirrors, the rate of cancer is 2 times higher than that of adenoma, and the rate of adenoma is 6 times higher. Because fiber sigmoscopy is easy to grasp, it has been widely used in high-risk populations. Endoscopy, except for naked eyes and biopsy. In addition to pathological diagnosis, it is also possible to remove the pedicled lesions in different parts. It is difficult to determine the X-ray examination. The microscopic examination is further confirmed. In addition to confirming the symptomatic patients, it is also used to screen asymptomatic people in high-risk groups. .

7, imaging diagnosis

The purpose of imaging examination is to detect infiltration and metastasis. The estimation of infiltration depth is extremely important. The tumor metastasis rate is only 6% to 11% in the submucosal, 10% to 20% in the submucosal, and the full infiltration can be used. Up to 33% to 50%.

(1) Double contrast of colonic gas sputum:

It is an important method for examination of colonic lesions, but it should not be used as a general survey of the population. The contrast of double gas sputum contrast is better than that of single sputum contrast test. The detection rate of the former can reach 96%, similar to colonoscopy, Thoeri and Menuk report double The contrast rate of small colon polyps was 11.7%, while that of single barium angiography was 45.2%. The detection rate of polyps was 87% and 59%, respectively. In experienced patients, the rate of double angiography was 96. %, close to the colonoscopy results, but X-ray angiography also has shortcomings, which can cause false negatives due to fecal or sigmoid colony, and the false negative rate can reach 8.4%.

Checkpoints: 1 Intestinal preparation should avoid cleansing the intestines, and use a slag-free diet plus oral laxatives to remove the feces.

2 Before injecting 70%80% of barium sulfate, the drug is injected intravenously (654-2), so that the colon is in a low-tension state. Under the fluoroscopy, the sputum can be displayed until it shows hepatic collateral, and then the gas is inflated to reach the bloating sensation.

3 Subjects change position, take supine and left, right oblique position, standing position and supine position, right front oblique position, etc. to fully display the left half, right half, cecum and other parts, pay attention to observe whether there is filling defect, intestinal wall stiffness and Stenosis, sputum, diagnosis should pay special attention to the presence or absence of signs of malignant transformation, such as: the presence or absence of stiffness in the head of the polyp, ulceration, basal intestinal wall shrinkage and other signs (Figure 4); in the presence of cancer, observe the presence or absence of other parts of the colon Small polyps; more polyps in those under 40 should consider familial adenoma.

(2) CT scan:

The observation of morphological changes in the colon cavity is generally better than CT, but CT is helpful to understand the degree of cancer invasion. CT can observe the thickening of the intestinal wall, prominent, but sometimes it is difficult to identify benign And malignant, CT's greatest advantage is to show the involvement of adjacent tissues, lymph nodes or distant organs with or without metastasis, thus contributing to clinical staging, the CT staging method proposed by Moss et al:

Phase 1: The thickness of the digestive tract wall is normal (usually 5 mm), and the polypoid lesions protrude into the cavity.

Phase 2: The tube wall is locally thickened, showing a uniform plaque or nodular appearance, without wall expansion.

Phase 3: Local thickening of the wall, direct invasion of surrounding tissues; may have local or regional lymph node involvement, but no distant metastasis.

Phase 4: There are distant metastases (such as liver, lung, distant lymph nodes).

Because CT examination is helpful to understand the scope of the tumor, contribute to preoperative staging, estimate the scope and formulate treatment plan, it is also one of the indicators to estimate the prognosis. Therefore, CT examination has been used as one of the routine examination methods, but there are materials for CT. The correct rate of pre-staged staging is 48%-72%, and the correct rate of lymph node metastasis is estimated to be 25%-73%. It seems difficult to be a routine examination of staging, but the detection rate of liver or metastatic nodules is more meaningful.

(3) MRI:

The diagnosis of intestinal tumors is still unclear. MRI can make up for the deficiency of CT diagnosis. MRI is easy to understand the infiltration of fat around the rectum, so it is helpful to find or identify the third stage patients.

Diagnosis and differentiation of sigmoid colon cancer

Diagnosis can be performed based on clinical performance and laboratory tests.

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