Carcinoma of colon and rectum is a disease that causes cancerous lesions in the colon or rectum tissue, and is a common malignant tumor in the gastrointestinal tract, with the incidence of rectum, sigmoid colon, cecum, ascending colon, descending colon and transverse colon from high to low, and in recent years, it has a tendency to develop proximal (right colon). Its pathogenesis is closely related to lifestyle, genetics, colorectal adenoma, etc. The age of onset tends to be aging, and the male-to-female ratio is 1.65:1.
According to the latest data from the Annals of Internal Medicine 2022 (Ann Transl Med 2022), 76.9% of colorectal cancer patients in mainland China are in the middle and advanced stages when they are first diagnosed. Colorectal cancer is currently the second most common malignant tumor and the fourth leading cause of mortality in mainland China, and the standardized incidence and mortality rate of all cancer species are still increasing. Globally, the disease burden of colorectal cancer is also severe.
Causes of colorectal cancer
It has been known that it may be related to the following precancerous lesions and some factors:
(1) In many clinical practices, it has been found that colon polyps can be malignant, among which papillary adenomas are the most prone to malignant transformation, up to 40%; The incidence of carcinogenesis is higher in patients with familial polyposis, indicating that colon cancer is closely related to colon polyps.
(2) Some chronic ulcerative colitis can be complicated by colon cancer, and the incidence rate may be 5~10 times higher than that of the normal population. The cause of colon cancer may be related to the chronic inflammatory stimulation of the colonic mucosa, and it is generally believed that cancerous transformation occurs through the inflammatory polyp stage in the process of inflammatory proliferation.
(3) Cases of schistosomiasis complicated by colon cancer are not uncommon in China, but the causal relationship is still debated.
(4) According to the statistics of the World Epidemiological Survey of Oncology, the incidence of colon cancer is high in North America, Western Europe, Australia, New Zealand and other places, but low in Japan, Finland, Chile and other places. The study believes that this geographical distribution is related to the dietary habits of residents, and the incidence is higher in those who eat high-fat diets.
(5) The incidence of colon cancer may be related to genetic factors, which has attracted more and more attention.
Clinical manifestations of colorectal cancer
Colorectal cancer may have no obvious symptoms in the early stage, and the following symptoms may appear when the disease progresses to a certain extent:
1. Sudden change in bowel habits: mostly changes in the frequency of bowel movements or fecal properties, such as the original stool once a day, and the recent sudden stool 3~4 times, or diarrhea and constipation alternately, and the change lasts for more than 2-3 months, it needs to be paid attention to.
2. Changes in the shape of the stool: Polyps press on the stool, and the shape of the stool will become thinner or flattened, with grooves or blood marks in the middle.
3. Mucus and bloody stool: This is the earliest and most common manifestation of colorectal cancer, and left colon cancer is more likely to be observed. Mild cases may present with only occasional small amounts of bleeding, while severe cases may present with mucobloody stools, mucopus-bloody stools, or bloody stools.
4. Abdominal pain: The pain is paroxysmal cramping, which lasts for a few minutes, and the pain is painful to feel that there is gas channeling, followed by gas, and then the pain suddenly disappears. It may present as discomfort or vague pain in the right lower quadrant, accompanied by abdominal distention, hyperperistalsis, constipation, and obstruction of gas. When older people develop this symptom, colorectal cancer should be considered first.
5. Abdominal mass: Some patients can feel the abdominal mass, which is irregular in shape, and some masses can move with the intestinal tube.
People at high risk of colorectal cancer
The definition of "colorectal cancer high-risk population" varies slightly from one organization to another, with the main reference in mainland China being defined as "those who meet any of the following criteria":
- positive for fecal occult blood
- Family history of colorectal cancer in first-degree relatives
- History of the adadenocele of the person's body
- History of Cancer
- Changes in bowel habits
- Any 2 of the following: chronic diarrhea, chronic constipation, mucus and bloody stools, chronic appendicitis or appendectomy, chronic cholecystitis or cholecystectomy, and long-term mental depression with alarm signals
Colorectal cancer screening
Cancer screening is a window period between "tumor germination" and "tumor trouble". It can take up to 10 years for polyps to evolve into bowel cancer. If bowel cancer can be detected early and treated in time, the 5-year survival rate of patients can reach more than 90%, and the cure is basically achieved. At present, about 80% of colorectal cancer patients are found to be in the middle and advanced stages of clinical development, and nearly half of the patients have a survival time of no more than 5 years.
Colorectal cancer mortality has dropped by more than 40% in recent decades, thanks to early screening. The 2018 Expert Consensus on Early Diagnosis and Screening of Colorectal Tumors in China recommended that the screening population be the general population aged 40-75 years, with priority given to the urban population (the incidence of bowel cancer in urban areas is significantly higher than that in rural areas).
There are three main types of screening for bowel cancer: stool, imaging and endoscopy. Colonoscopy remains the gold standard for colorectal cancer screening.
However, patients should not rest easy when a colonoscopy is normal or an adenoma is found and removed. Statistics show that 5 years after colonoscopy removal of adenoma, the risk of adenoma recurrence/metachronous adenoma is more than 80%. Therefore, regular colonoscopy monitoring and follow-up should be performed in combination with the individual's colorectal cancer risk and adenoma characteristics to detect recurrence of adenoma or metachronous colon adenoma (carcinoma) in a timely manner.
At present, there are many studies on colorectal cancer screening and early diagnosis markers, and new markers are emerging one after another, with more reference value, and research progress with clinical application prospects is constantly emerging, such as fecal enterobacteria detection (with Nucleatella, Clostridium symbiotics), multi-target fecal occult blood test and DNA detection technology, long non-coding RNA, etc.
Prevention of colorectal cancer
Strictly speaking, the prevention of colorectal cancer includes chemoprevention, screening and early diagnosis, endoscopic removal of adenoma and follow-up, dietary adjustment, weight loss, etc. According to different purposes, prevention can be divided into primary prevention (used before the occurrence of adenoma to prevent the occurrence of adenoma) and secondary prevention (used after adenoma removal to prevent adenoma recurrence).
Primary chemoprevention includes folic acid, aspirin, and statins as prescribed.
Secondary prevention refers to chemoprevention of recurrence after removal of the adenoma. This includes the use of berberine hydrochloride (berberine), calcium, and/or vitamin D and metformin as prescribed.
It has been suggested that the prevention of colorectal cancer should be started from multiple perspectives, including the regulation of diet, intestinal microecology and other environmental factors, but there is still a lack of interventional research in this area. Some scholars believe that the current high incidence of early-onset colon cancer is inseparable from excessive intake of emulsifiers, trans fatty acids, acrylamide, nitrites, etc., and it is recommended that diet should be controlled.
Intestinal microbiota is a new target for the diagnosis and treatment of colon cancer, which has attracted great attention in recent years. It is also expected that fecal transplantation, probiotic-prebiotic supplementation, or dietary interventions to eliminate pathogenic bacteria will help prevent colorectal cancer.
In order to assess an individual's risk of colorectal cancer more accurately and personally, a variety of risk stratification systems have been developed. For example, the Asia-Pacific Colorectal Cancer Risk Score includes indicators such as age, gender, family history, and smoking (the modified score adds a "BMI" indicator), and each indicator is given a certain weight to determine the colorectal cancer risk based on the total score.
It is also important to note the influence of genetic and environmental factors on the risk of colorectal cancer, especially those that can be modified. Some of them play a protective role like physical activity, healthy diet, certain medications, while some carry a higher risk like smoking, alcohol consumption, unhealthy food, obesity, etc.