- Large Intestine Structure and Cancer Formation Process
The large intestine is the last part of the digestive system. After the food taken orally is exposed to various digestive events in the stomach and small intestines, the remaining part reaches the large intestine (feces-feces). Liquid absorption continues without digestion in the large intestine. The large intestine is responsible for storing and excreting feces. The large intestine is approximately 1.5 meters long and ends with the anal canal.
The large intestine wall (from inside to outside); consists of 4 layers: mucosa, submucosa, muscular layer and serosa. Colon cancers often develop from the inner layer of the mucosa. Mucosal cells take part in fluid absorption and secrete mucus. The cells here die after a certain lifespan and are replaced by new cells. Cancer cells form in these cells after mutations in the gene structure and various environmental factors. These cells, unlike normal cells, multiply faster and do not die. The cancer cells formed here multiply and reach the vessels and lymph channels in the deeper layer and begin to spread to more distant organs. This is called metastasis.
- Incidence of Colon Cancer
1 million people are diagnosed with colon cancer annually in the world and approximately 500 are diagnosed with colon cancer. Thousands of people lose their lives due to this disease. The incidence varies between geographical regions and regions. It is more common in developed countries. Approximately 7-8% of all cancers in Turkey are colon cancer. The average age of occurrence is 60. Although the cause of colon cancer is not fully known, some risk factors have been identified that increase its incidence. Some well-known risk factors: Advanced age, family history, presence of adenomatous polyps in the colon, inflammatory bowel disease (especially ulcerative colitis) and some genetic diseases (such as FAP). Apart from this, less effective risk factors such as fiber-poor, high-calorie diet, diabetes, cholecystectomy, smoking, obesity, and cardiovascular disease have been accused in various studies.
;Symptoms vary depending on the location and stage of the cancer. bowel habit changes in blood pressure, diarrhea, constipation, feeling of incomplete evacuation (tenesmus), blood in the stool (bright or dark red), thinner stools than usual, general abdominal discomfort. Complaints such as (gas, cramps, bloating), weight loss without a known reason, constant fatigue, nausea and vomiting may be related to colon cancer. These complaints need to be thoroughly investigated, especially in people over 50 years of age.
- How Does Cancer Start?
The disease first begins in the mucosa, It then reaches the blood vessels and lymph channels in the submucosal tissue. As the tumor grows and moves outward from within the wall, it also tends to spread to more distant areas via lymph and blood vessels. As the tumor progresses in the wall, the chance of spreading to regional lymph nodes and distant organs increases. The degree of spread of the tumor to the wall(T), the number of involved lymph nodes (N) and the presence of metastasis (M) determine the stage.
There is a direct relationship between the stage of the disease and life expectancy. While 5-year survival is 80% in stages 1-2, it drops to 10% in stage 4. Screening programs have been developed to detect the disease at an early stage. Screening aims to reduce disease-related mortality (increase in life expectancy) and increase complete cure. The aim here is to detect the disease when it is asymptomatic or to detect and treat precancerous lesions (such as adenomatous polyps). With the colonoscopic treatment of pre-cancerous lesions and the coloscopic treatment of very early cancers (Instant carcinoma, some of the T1 tumors), it is possible for patients to be protected from colorectal cancer and to be fully cured.
It is possible for patients to be hidden in the stool for screening. Blood transfusion (FOBT), rectosigmoidoscopy, and colonoscopy are the most frequently preferred methods. Efficiency, reliability and cost are the most important problems in screening. Each country has its own screening program. In Turkey, the Ministry of Health recommends screening the population between the ages of 50-70. In trama, recommend FOBT (fecal occult blood - 3 times) and colonoscopy every 10 years. . This screening program is valid for standard individuals, but the screening program is carried out in different ways for individuals with familial-genetic predisposition. For example For a person whose mother was diagnosed with colon cancer at the age of 50, it is recommended to start the screening program at the age of 40-42.
The diagnosis of colon cancer is often made by colonoscopic examination and biopsy. Subsequently, the patient's imaging examinations (USG-CT-MRI) determine the stage of the disease. However, in emergency cases (such as ileus), the diagnosis can be made immediately.
- Treatment Stages
Surgical treatment: The aim of the treatment is a wide resection, including the tumor area and the lymph nodes draining this area. is the removal of the tumor. Continuity of the remaining intestine is often ensured by anastomosis. Sometimes the intestine can be removed permanently (lower rectum tumors, anal canal tumors) and sometimes temporarily (such as rectal tumor, emergency cases) (ilostomy, colostomy) strong>. There have been some changes in colorectal surgery in recent years. There are many innovations in this regard, especially in rectal surgery. Resection plans are better defined and stomas are fewer. More satisfactory results have begun to be obtained with chemotherapy and radiotherapy before surgery. On the other hand, the organs where the tumor has spread are removed more radically than before. (Liver resections, multiple organ resections, etc.). Metastasis to the liver is common in colorectal cancers. While surgery was not considered for metastatic disease in the past, recently 25% of patients with liver metastases can be treated surgically.
In terms of oncological surgery, it has become comparable to chemotherapy.
- Chemotherapy. :Chemotherapy is not recommended for early stage tumors (Stage 1-2). The effectiveness of chemotherapy has been demonstrated in advanced stages of cancer, especially in stage 3-4 disease. Chemotherapy provides an approximately 30% reduction in cancer-related death. Better and more effective results are obtained with newly developed chemotherapeutic agents. The real innovation in this field is the very good responses to chemotherapy combined with radiotherapy, especially in rectal cancer.
- Radiotherapy: Radiotherapy (radiation therapy) has no place in colon cancer. However, radiotherapy is used after surgery, especially in rectal cancer. It can be given before and after and makes a positive contribution to survival by reducing tumor recurrence. In recent years, it has been shown that preoperative radiotherapy and chemotherapy are more effective in rectal tumors. This treatment also reduced the permanent stoma rate of patients.
As a result, colorectal cancers are the 4th most common cancer in men and the 3rd most common in women in Turkey. Early diagnosis with screening methods in the asymptomatic phase increases life expectancy and the chance of curing the disease. Advances in treatment and surgery contribute to the reduction in mortality. Early diagnosis and treatment should be the main goal in colorectal cancer, as in many cancers.
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