Causes and Treatment of Large Intestine Cancers
What is large intestine (colorectal) cancer?
The colon and rectum form the part of the digestive system called the large intestine. It is approximately 1.5 meters long in total. Partially digested food moves from the small intestine to the colon. The colon separates water and minerals from food and stores the rest to be excreted through the anus. Cancer that starts in the colon is called colon cancer, and cancer that starts in the rectum is called rectal cancer. Colon and rectum cancers develop from the cells that form the layer covering the inner surface of these organs. According to the statistics of the Ministry of Health, it is among the top 5 most common cancers. Although they can be seen at any age, they are most commonly observed after the age of 50. The average age of occurrence is 63. There is not much difference between men and women in terms of frequency. When colorectal cancer spreads beyond the colon and rectum, cancer cells can often be found in nearby lymph nodes. If cancer cells can reach these lymph nodes, they can reach other glands, the liver and distant organs.
What are the risk factors of colorectal cancer?
The exact cause of colorectal cancer is unknown. There are some risk factors for colorectal cancer:
Age: Colorectal cancer is generally seen in the elderly. 90% of patients are diagnosed after the age of 50. The average age is in the 60s.
Polyps: Polyp is a benign tumor. They originate from the inner wall of the colon or rectum. It is common in people over 50 years of age. Some polyps (adenomas) can become cancerous. In this case, the polyp should be removed and checked at regular intervals due to the risk of cancer. Early diagnosis and removal of polyps reduces the risk of colorectal cancer.
Family history of colorectal cancer: If a person has a history of colorectal cancer in close relatives (mother, father, sister or brother, children), the risk of contracting this disease increases, especially at a younger age.
Genetic disorders: Changes in certain genes increase the risk of colorectal cancer. It accounts for 2% of all colorectal cancer cases. It is caused by changes in the HNPCC gene. Colorectal cancer develops in 75% of patients with altered HNPCC genes, and the average age at diagnosis of cancer is 44 years.
Familial adenomatous polyposis (FAP): It is a rare condition characterized by hereditary polyps in the colon and rectum. It is caused by changes in a special gene called APC. The treatment is to remove the entire large intestine. If FAP is not treated, colorectal cancer develops around the age of 40. FAP accounts for less than 1% of all colorectal cancer cases.
Having had colorectal cancer before: A person with a history of colorectal cancer may develop colorectal cancer again. The risk of colorectal cancer is increased in women with a history of ovarian, uterine and breast cancer.
Ulcerative colitis or Crohn’s disease: The risk of colorectal cancer is increased in those with this inflammatory disease of the intestine. These people have a 10-fold increased risk compared to the normal population.
Diet: The risk of colorectal cancer is increased in those who eat a diet rich in animal fat and low in calcium, folate and fiber. A diet low in fruits and vegetables also increases the risk.
Smoking: The risk of polyps and colorectal cancer is increased in patients who smoke.
How can I protect myself from colon cancer?
In addition to screening methods, there are also some steps to reduce the risk of colon cancer. For example, physical exercise, losing excess weight, not smoking, and consuming high-fiber, low-fat foods are a few of them.
What are the symptoms of large intestine cancer?
A patient who develops colorectal cancer may experience changes in bowel habits, diarrhea, constipation, a feeling of incomplete emptying of the intestines, blood in the stool (bright or dark red), thinner stools than usual, general abdominal discomfort (gas, cramps, bloating), weight gain for no known reason. Complaints such as fatigue, constant fatigue, nausea and vomiting may occur.
Signs and symptoms of colorectal cancer vary depending on the stage of the tumor and the location of the tumor. While the tumor does not cause any symptoms as it grows into the intestine, it may cause symptoms ranging from the patient being unable to pass gas and feces when the intestine is completely blocked. Symptoms observed in tumors on the right side of the large intestine are unnoticeable blood loss with stool and anemia due to this bleeding, weakness, shortness of breath, easy fatigue, and change in defecation habits. Other symptoms include occasional attacks of constipation and diarrhea, abdominal pain, abdominal bloating, and weight loss. The most common location of large intestine tumors is the left side, which is one of the narrow parts of the large intestine. That’s why intestinal obstructions are more common in left-sided tumors.
The most common finding in tumors on the rectum side, that is, in the part close to the anus, is blood contamination in the stool. One of the situations to be considered here is that blood is observed in the stool in the disease called hemorrhoids, and the person may confuse this situation and delay the diagnosis and treatment. Changes in defecation habits, thinning of stool diameter, constipation, incomplete evacuation after defecation, and abdominal bloating are other observed findings. When you suspect these findings, you should consult a doctor. One of the undesirable conditions of late-stage colon cancer is complete obstruction of the intestine. Other possible situations that may occur include serious bleeding as a result of the collapse of the wall of the large vessel, the tumor perforating the intestinal wall, the spread of microbes in the large intestine to the abdominal membrane, and fluid accumulation in the abdominal cavity.
These symptoms may not always be due to cancer. Other health problems may cause these symptoms. However, people with any of these are recommended to consult a doctor for early diagnosis and treatment. Generally, there is no pain in the early stages of cancer. Seeing a doctor without waiting for pain is important in the early diagnosis of cancer.
How is colon cancer diagnosed?
Like other cancers, colon cancers may not cause symptoms until they grow larger. Therefore, the aim should be to detect the tumor before there are any symptoms of cancer. Screening a person for cancer before symptoms develop helps in early recognition of polyps and cancer. Early recognition and removal of polyps can prevent colorectal cancer. When diagnosed early, treatment of colorectal cancer may be more effective. Therefore, people over the age of 50 should be monitored and people at increased risk for colorectal cancer should be included in an earlier screening program.
Screening tests used in early diagnosis are:
Fecal occult blood test: Since cancers and polyps bleed, it is possible to detect small amounts of blood in the stool with this test. However, non-cancerous bleeding causes such as hemorrhoids can also lead to a positivity in this test. If the properly performed fecal occult blood test is positive, the colon must be examined endoscopically.
Sigmoidoscopy: The last 60 cm of the intestine, called the rectum and sigmoid colon, is visualized. If a polyp is detected, it allows it to be removed with a procedure called polypectomy.
Colonoscopy: The inner wall of the entire colon is visualized, and polyps, if any, can be removed.
Finger examination of the rectum: The doctor examines the rectum with his gloved finger, lubricating it with vaseline.
Double-contrast barium colon radiography: Allows to show the tumor with films taken after the administration of a white opaque substance from the anus. It is useful in showing large tumors, but is not as reliable as colonoscopy.
How is screening for colorectal cancer?
Patients who are not in risk groups,Fecal occult blood screening is recommended starting from the age of 50, and over the age of 50, sigmoidoscopy is recommended at least every 5 years and colonoscopy is recommended every 10 years. In some countries, the age for screening for colorectal cancer has been lowered to 45.
Patients in the risk group;Patients who have had polyps removed before should have a repeat colonoscopy within 1-3 years after this procedure. Those whose close relatives, such as parents, have been diagnosed with colorectal cancer should start screening before the age of 40 or at the latest 8-10 years before the age at which the relative was diagnosed.
Genetic testing should be done for hereditary non-polyposis colorectal cancer. People with the disease called familial adenomatous polyposis (FAP) should receive genetic counseling and be followed up with colonoscopy starting from the age of 10-15. People with breast and female genital organ cancer should have colonoscopy periodically after the age of 40, and people with ulcerative colitis should have periodic colonoscopy after diagnosis.
In people with colorectal cancer symptoms and signs, it is necessary to determine whether these are due to cancer or another cause. If an abnormal finding is detected in the examinations (such as a polyp), a biopsy is required to detect cancer cells. The tissue removed by the pathologist is examined under a microscope for the presence of cancer cells.
What is the treatment for colon cancer?
Surgery, radiation and chemotherapy are the main treatment methods used in the treatment of colon cancer. Treatment varies depending on the location and stage of the tumor. Before starting treatment, patients can question the stage of the disease, treatment options, treatment side effects, negative effects of the treatment on their normal lives, the cost of the treatment, and the existence of new clinical trials that may be suitable for them.
Surgery: Surgical treatment is the main step in the treatment of cancer. But for this to happen, the cancer must not have spread to distant organs (liver, lung, brain, bone, etc.). In the surgical method, the tumor part is removed along with the surrounding healthy tissue. In addition, the tissue called mesentery and lymph nodes that connect the intestine to the body are also removed. In rectal cancers, the tumor is removed along with a part of the left side of the large intestine and the two ends are joined together. In cases where reattachment is not possible, the surgeon attaches the end of the intact intestine to the abdominal wall and closes the other end. This is called a colostomy. Feces are removed through special colostomy bags. In most patients, this condition is temporary and is closed after the colon or rectum heals after surgery. Colostomy may be permanent in patients with tumors in the lower rectum, very close to the anus. In recent years, surgical treatment has now been applied, especially for intestinal tumors that have spread to the liver and lungs, where the tumor in that area is completely removed, and the results are very satisfactory.
Chemotherapy: Chemotherapy is the use of anticancer drugs to kill cancer cells. It is called systemic treatment because the drugs pass into the bloodstream and kill cancer cells in the body. It is a frequently used treatment in some stages of colon cancer and in cases where it has spread to another part of the body. Anticancer drugs can be given orally or intravenously. Patients can receive these treatments in the hospital as an outpatient or rarely as an inpatient. Patients can receive chemotherapy alone or in combination with surgery and radiotherapy.
Radiation Therapy: Also called radiotherapy. It is a local treatment that causes the destruction of tumor cells with ionizing radiation. The aim is to kill cancer cells in the treated area with high-energy rays. Radiotherapy may be given before surgery to shrink the tumor or along with chemotherapy to prevent recurrences after surgery. Radiotherapy is generally used in rectal cancers and some stages of them.
