So what are the causes of colorectal cancer?
1.Family inheritance
Hereditary colorectal cancer occupies an important proportion in the colorectal cancer system. Clinically, based on the presence or absence of polyposis, hereditary colorectal cancer can be divided into two categories: familial hereditary polyposis and familial hereditary non-polyposis. The former includes familial adenomatous polyposis, Turcot syndrome (glioma polyposis syndrome), and the latter includes Peutz-Jeghers syndrome (melanoma-gastrointestinal polyposis syndrome), familial juvenile polyposis, Cowden
syndrome (multiple dysplasia syndrome), Bannayan-Ruvalcaba-Riley syndrome, and others. Both types of hereditary colorectal cancer are inherited in an autosomal dominant manner. It has been found that hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis account for about 5-15% and 5% of colorectal cancers, respectively.
The diagnostic criteria for familial hereditary nonpolyposis colorectal cancer are.
(1) At least 3 persons in the family are pathologically confirmed with colon cancer and 1 of them is an immediate relative of the other 2 persons.
(2) It must involve 2 consecutive generations.
(3) At least 1 person has colorectal cancer earlier than 50 years of age; (4) Familial adenomatous polyposis is excluded.
Familial polyposis, a heterozygous autosomal dominant colon disease, can have 100 or more adenomatous polyps covering the colon and rectum, and a mutated dominant gene (FAP) on the long arm of autosome 5 is the causative factor. It has been found that adenomatous polyps often appear at the age of 10-15 years and if left untreated, almost all patients will develop malignancy by the age of 45 years.
2.Dietary factors
Studies have found that people with high fat and low fiber diets have a higher chance of developing colorectal cancer. The University of Cambridge has published a large study on diet and cancer, in which 400,000 people were surveyed, and the results showed that a high-fiber diet can effectively reduce the risk of fatal cancer by
The results showed that a high-fiber diet was effective in reducing the risk of developing deadly cancers, especially colorectal cancer, by 40%. Dietary fiber can stimulate intestinal peristalsis and shorten the time it takes for food to pass through the intestinal tract, reducing the chances of carcinogens in the stool coming into contact with the intestinal mucosa and expelling stools and toxins from the body as soon as possible.
Some studies have confirmed that the incidence of colorectal cancer among Chinese and Japanese is significantly lower than that in the United States, but the incidence of colorectal cancer among the first generation of immigrants to the United States has increased significantly, and the incidence of colorectal cancer among the second generation is close to that of Americans. This epidemiological feature of immigrants suggests that the incidence of colorectal cancer is closely related to environmental factors, especially dietary factors. It is well known that, unlike Chinese and Japanese, Americans prefer to eat high-fat foods and often have insufficient fiber intake.
In addition, in addition to fiber being effective in preventing colon cancer, fruits and vegetables contain vitamins (A, C, D, E, folic acid) and trace elements that may help protect the intestinal mucosa, and some studies have shown that they can convert colonic epithelial hyperplasia to normal in adenoma patients. However, it is still unclear what the specific mechanism is.
3, bad lifestyle habits
Studies have found that patients suffering from colorectal cancer often have bad habits. The common bad habits include.
(1) Lack of exercise;
(2) Smoking and alcohol abuse;
(3) Excessive stress in life.
In addition to poor diet control, obese patients often lack exercise, and many people think that exercise will make people more easily fatigued. Almost all people who exercise regularly and scientifically can feel energetic and rarely feel fatigued. Adhering to quantitative and scientific exercise can effectively improve many important physiological functions of the human body, and can also better control body weight, promote intestinal peristalsis and help to discharge stool, so adhering to exercise is beneficial to the prevention of colorectal cancer.
Smoking is a proven risk factor for colorectal adenoma, which is a high-risk precancerous lesion for colorectal cancer.
The journal Am J Clin Nutr has published a study of more than 87,000 women and 47,000 men.
The Am J Clin Nutr journal published the results of a study of more than 87,000 women and 47,000 men that sought to find a link between colorectal cancer and alcohol. In this study, 1,801 colorectal cancer cases were diagnosed through follow-up since 1980. The results of the study showed that people with a family history of alcohol consumption who consumed more than 30 grams of alcohol per day had a significantly increased risk of colorectal cancer. Subjects without a family history of alcohol consumption did not show a correlation between alcohol intake and colorectal cancer.
Excessive stress in life may lead to severe anxiety and depression, which can cause increased secretion of adrenaline and adrenocorticotropic hormones, resulting in slower intestinal motility and prolonged retention of food residues in the intestinal lumen, allowing more carcinogens to be absorbed, leading to colorectal cancer. In addition, mental anxiety and depression may lead to the dysfunction of immune function of the body, which makes its ability to monitor and clear certain mutated epithelial cells weakened.
4, precancerous lesions
(1) colorectal polyps (adenomatous polyps): It is generally believed that most colorectal cancers originate from adenomas, so adenomatous polyps are regarded as precancerous lesions. Generally, the larger the adenoma, the more irregular the morphology, the higher the villi content, and the heavier the epithelial heterogeneous hyperplasia, the greater the chance of cancer. Studies have confirmed that the steps of colorectal carcinogenesis are normal intestinal epithelium → early hyperplastic changes → microadenoma → early adenoma → middle adenoma → late adenoma → colorectal cancer → cancer metastasis. In this process, oncogenes and oncogenes play a crucial role, and gene mutations are seen as the molecular basis of colorectal carcinogenesis. So, how long does it take for an adenomatous polyp to transform into colorectal cancer? Studies have found that the chances of adenoma developing into cancer in 5, 10, and 20 years are 3%, 8%, and 24%, respectively.
(2) Inflammatory bowel disease: ulcerative colitis can become cancerous, and the cancer rate is related to the disease duration, the longer the disease duration, the higher the cancer rate; it is also related to age, the younger the age of onset, the higher the cancer rate.
5.Other factors: gallbladder removal.
It has been found that the incidence of colorectal cancer increases after cholecystectomy, and the possible mechanism is that the primary bile acid content in stool decreases and the secondary bile acid content increases after cholecystectomy. Primary bile acids are synthesized in the liver, including bile acid (CA) and goose deoxycholic acid (CDCA). A portion of primary bile acids is deoxygenated by bacteria to form secondary bile acids, including deoxycholic acid (DCA), lithocholic acid (LCA) and trace amounts of ursodeoxycholic acid (UDCA). Secondary bile acids of
LCA can increase the incidence of colorectal cancer, while DCA can be converted to methylcholanthrene, which is a strong carcinogenic substance.
After understanding the causes of colorectal cancer, how to prevent it?
1. Change the bad habits, control the weight within the standard range, and insist on aerobic exercise, which is recommended 4~5 times a week. Each time lasts 20~40 minutes.
Quit smoking and drinking, maintain an optimistic attitude, and actively mediate life and work stress.
2. Reasonable adjustment of diet structure, no pickled, smoked or baked products, no moldy food, low-fat diet, scientific distribution of vegetables and fruits and other fiber diet.
3. Actively treat precancerous lesions, such as adenomatous polyps, ulcerative colitis, colorectal cancer is not formed from normal cells in one leap, it has a process of lesion development, which takes 5~20 years or even longer, so early detection and early treatment can effectively prevent the occurrence of colorectal cancer.
4. Those who have high risk factors and family history of colon cancer should pay more attention to prevention, and it is recommended to check colonoscopy once a year.
Due to the rapid development of endoscopy, 80%-90% of intestinal polyps that have not developed into colorectal cancer can be removed through endoscopy, which is safer and faster recovery, avoiding the trauma of surgical opening, which provides favorable conditions for the prevention and early treatment of colorectal cancer.
5. Studies show that long-term users of NSAIDs have a reduced incidence of colorectal cancer, and taking small doses of aspirin daily can reduce the relative risk of colorectal cancer. However, aspirin also has drug side effects, such as it may lead to gastric mucosal erosion, bleeding and ulcers, so it should be used with caution and a specialist should be consulted when it is needed.