Colorectal cancer (CRC) is one of the most common malignant tumors in human beings, with the fourth highest incidence of malignant tumors in the world, involving about 1 million people annually and nearly 500,000 deaths annually. In Europe and the United States, colorectal cancer is the second leading cause of death from malignant tumors. In recent years, due to westernization of life pattern, the incidence and mortality rate of colorectal cancer in China have been increasing year by year, and the age of onset is also significantly advanced.
High risk factors of colorectal cancer
Although colorectal cancer can occur in all age groups, 90% of patients occur above the age of 40. The risk of developing cancer increases with age, and most patients are diagnosed with the disease in their 50s and 60s.
The following groups are generally considered to be at high risk for colorectal cancer.
(1) Patients with adenomatous polyps of the colorectum.
(2) Patients with ulcerative colitis.
(3) Patients with a family history of colorectal cancer or a history of breast, ovarian or endometrial cancer have an increased risk of developing colorectal cancer.
Development of colorectal cancer
Most colorectal cancers develop from a single cell or group of cells in the intestine. These cells begin to differentiate and grow into a non-cancerous (benign) bulky mass called a polyp. Polyps appear as protrusions or projections in the lining of the bowel. As these polyps get larger, they may become cancerous, infiltrating the intestinal wall or metastasizing to other parts of the body. The change from benign polyps to malignant tumors is associated with changes in the genes that control each cell. These changes may be inherited or arise spontaneously.
Manifestations of colorectal cancer
Many colorectal polyps and cancers are asymptomatic until they become quite large. It is important to detect tumors when they are not yet large or have good activity. Therefore, screening for asymptomatic people is recommended to detect these bulges or polyps early.
The most common symptom of colorectal cancer is bleeding during bowel movements (blood in stool, dripping blood after stool, or blood on toilet paper). Changes in bowel habits, such as new constipation or persistent diarrhea will need to be checked by your doctor. Abdominal pain and unexplained weight loss may be a sign of cancer progression.
Prevention of colorectal cancer
Although colorectal polyps and cancers may not be symptomatic in the early stages, simple screening can detect many bulky growths and polyps. Colorectal polyps can be detected and removed with sigmoidoscopy and colonoscopy, reducing the risk of their development into cancer.
Diet plays a role in preventing colorectal cancer, although it is not known how much of a role it plays. A diet high in fiber such as grains, fruits and vegetables, and low in fat will lower your risk of cancer. A high-fiber, low-fat diet will also lower your risk of heart disease, diverticula, constipation and hemorrhoids.
Screening for colorectal cancer
Men and women should be screened annually for anamnesis and fecal occult blood starting at age 40 even if no risk factors are present. sigmoidoscopy should be performed to examine the lower bowel starting at age 50. If normal, it needs to be repeated every five years. In general, people with risk factors should have a barium enema every five to ten years or a colonoscopy every ten years.
People at high risk for colorectal cancer should have a full colon and rectal examination. Colonoscopy is the best method, but sometimes a barium enema with a removable sigmoidoscope is sufficient. In general, it is also necessary to review the test every five years. The timing of the first exam depends on risk factors. If more than one person in the family had colorectal cancer before age 50, then screening should begin at age 40 (or five years earlier than the age of diagnosis). If one parent has familial multiple polyps, screening should be started at 12-14 years of age. Individual screening programs for those with other risk factors such as inflammatory bowel disease (Crohn’s disease or ulcerative colitis) should be discussed with your doctor.
A family history of colorectal cancer or polyps or a personal history of colorectal cancer or adenomatous polyps should be screened by colonoscopy. Any polyps should be removed and rechecked every one to three years. If the test is normal, a colonoscopy should be performed once every three to five years. Women with breast, ovarian or uterine cancer should have a colonoscopy every three to five years starting at age 40.
Spread of colorectal cancer
Cancer spreads in two ways: direct growth and the distant spread of cancer cells called metastasis.
Direct growth: When a tumor grows, it may spread into or around the intestine. Eventually, the tumor will infiltrate the bowel wall and spread to adjacent organs such as other bowel segments, the abdominal wall, the bladder or the uterus.
Metastasis: Tumor cells are shed from the primary tumor and spread to other parts of the body through blood and lymphatic fluid. These cells can adhere to or grow in distant places such as lymph nodes around the intestine, liver or lungs. When colorectal cancer is surgically removed, the lymphatic tissue surrounding the tumor is also removed. A pathologist will look at the lymphatic tissue under a microscope to determine if there are tumor cells. If there are no tumor cells in the lymph nodes, there is a better chance of cure.
Treatment of colorectal cancer
These cancers should be removed with surgery. Surgery includes traditional open surgery and laparoscopic surgery. The segment of the bowel with the tumor and the associated blood vessels and lymph nodes are removed. In most cases, the bowel is reconnected to maintain normal bowel function. This reattachment of the bowel is called anastomosis. If the cancer has spread to the lymph nodes or other sites, adjuvant treatment such as chemotherapy and/or radiation therapy should be recommended.
Most larger tumors are removed transabdominally. Although the bowel will reconnect after surgery, if the tumor is close to the anal opening a total rectal and anal resection is required. In this case, a colostomy is required, with the fistula opening in the abdomen. In rare cases, a temporary colostomy is required if the tumor causes an obstruction of the bowel.
About laparoscopic colorectal cancer surgery
Laparoscopic surgery is used in 90% of colorectal surgeries in developed countries in Europe and America. Compared with traditional open surgery, laparoscopic colorectal cancer surgery is less traumatic to the patient’s tissues, has less systemic reaction, less impact on the immune system, less pain, faster patient recovery, and can get out of bed early, resume diet, and shorten the time of inpatient treatment. For patients with malignant tumor, it reduces the damage to immune system, shortens the postoperative recovery time, and allows them to start postoperative radiotherapy and chemotherapy earlier, which undoubtedly creates more favorable conditions for improving the treatment effect of malignant tumor.
Staging of colorectal cancer
Staging provides a way to assess the chance of cure after cancer resection. Unlike other solid tumors, the size of colorectal cancer does not have a significant impact on the outcome. The staging system helps doctors to assess the extent of tumor infiltration: whether it has penetrated the bowel wall; whether it has spread to surrounding lymph nodes; and whether it has spread to distant organs or tissues. Tumors are divided into four stages. Staging is important because it can predict the chance of survival and can guide further treatment. If colorectal cancer recurs, it is usually within two years of surgery. The highest recurrence rate is within five years. stage I cancer patients have a five-year survival rate of greater than 90%, which is the type with the best cure rate.
The morphology of the tumor cells under the microscope is also important in determining treatment. This morphology is called “differentiation” and tumor cells are generally classified as highly differentiated, moderately differentiated and poorly differentiated. Tumor cells that are better differentiated are more effective than those that are poorly differentiated. Staging and differentiation help doctors decide whether to recommend radiation or chemotherapy after surgery.
Prognosis of colorectal cancer
Assessment of long-term outcome should be based on the stage of the disease. Patients with early stage cancer, where the tumor has not penetrated the intestinal wall and has not spread to lymph nodes or other sites, have a satisfactory outcome. Tumors that have spread to other sites or infiltrated lymph nodes have significantly improved chances of cure with a combination of surgery, chemotherapy, or radiation therapy.