Causes and Treatment of Colon Cancer

What is colon (colorectal) cancer?

The colon and rectum make up the part of the digestive system known as 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 the food and stores the remainder for excretion through the anus. Cancer that starts in the colon is called colon cancer, while cancer that starts in the rectum is referred to as rectal cancer. Colon and rectal cancers develop from the cells that line the inner surface of these organs. According to the statistics from the Ministry of Health, it is one of the top five most commonly seen cancers. While it can occur at any age, it is most often observed after the age of 50, with an average age of diagnosis being 63. There is little difference in incidence rates between men and women. When colorectal cancer spreads beyond the colon and rectum, cancer cells can generally be found in nearby lymph nodes. If cancer cells reach these lymph nodes, they can spread to other glands, the liver, and distant organs.

What are the Risk Factors for Colorectal Cancer?

The exact cause of colorectal cancer is not known. However, there are several risk factors associated with colorectal cancer:

• Age: Colorectal cancer is generally observed in older individuals. 90% of patients receive a diagnosis after the age of 50, with the average age being in the 60s.
• Polyps: Polyps are benign tumors that originate from the inner wall of the colon or rectum. They are common in people over 50 years old. Some polyps (adenomas) can become cancerous. In such cases, polyps should be removed due to the risk of cancer, and regular monitoring is necessary. Early detection and removal of polyps reduce the risk of colorectal cancer.
• Family History of Colorectal Cancer: If a person has a family history of colorectal cancer among close relatives (mother, father, siblings, or children), their risk of developing this disease, especially at a younger age, increases.
• Genetic Disorders: Changes in certain genes can increase the risk of colorectal cancer, accounting for 2% of all colorectal cancer cases. This occurs due to changes in the HNPCC gene. In patients with a mutated HNPCC gene, 75% develop colorectal cancer, with an average age of diagnosis of 44.
• Familial Adenomatous Polyposis (FAP): A rare condition characterized by hereditary polyps in the colon and rectum. It occurs due to changes in a specific gene called APC. The treatment involves the removal of the entire colon. If FAP is not treated, colorectal cancer can develop around the age of 40. FAP accounts for less than 1% of all colorectal cancer cases.
• Previous History of Colorectal Cancer: A person with a history of colorectal cancer may develop it again. Women with a history of ovarian, uterine, and breast cancer have an increased risk of colorectal cancer.
• Ulcerative Colitis or Crohn's Disease: Individuals with these inflammatory bowel diseases have an increased risk of colorectal cancer, with a risk that is 10 times higher than that of the general population.
• Diet: Diets rich in animal fats and low in calcium, folate, and fiber increase the risk of colorectal cancer. A diet low in fruits and vegetables also elevates this risk.
• Smoking: Smokers have an increased risk of developing polyps and colorectal cancer.

How Can I Protect Myself from Colon Cancer?

In addition to screening methods, there are several steps to reduce the risk of colorectal cancer. These include engaging in physical exercise, losing excess weight, not smoking, and consuming high-fiber, low-fat foods.

What are the Symptoms of Colon Cancer?

In a patient with developing colorectal cancer, symptoms may include changes in bowel habits, diarrhea, constipation, a feeling of incomplete bowel evacuation, blood in the stool (bright or dark red), thinner stools than usual, general abdominal discomfort (gas, cramps, bloating), unexplained weight loss, persistent fatigue, nausea, and vomiting.

The signs and symptoms of colorectal cancer vary based on the stage of the tumor and its location. While a tumor growing inward into the intestine may not present symptoms, it can lead to various symptoms if it causes a complete blockage of the intestine, preventing the passage of gas and stool. Symptoms observed in tumors on the right side of the colon include unnoticed blood loss in the stool and anemia, leading to fatigue, shortness of breath, and changes in bowel habits. Periodic constipation and diarrhea, abdominal pain, and bloating, as well as weight loss, are other symptoms. The most common location for colorectal tumors is on the left side, which is one of the narrower areas of the colon, thus leading to more frequent instances of bowel obstructions in left-sided tumors.

In tumors located near the rectum (anus), the most common symptom is blood in the stool. It is important to note that blood in the stool can also occur in conditions like hemorrhoids, which may lead individuals to confuse the two and delay diagnosis and treatment. Other observed symptoms include changes in bowel habits, narrowing of stool diameter, constipation, a feeling of incomplete evacuation after bowel movements, and abdominal bloating. If you suspect any of these symptoms, you should consult a doctor. One of the unwanted outcomes of late-stage colorectal cancer is a complete blockage of the intestine. Other possible complications include serious bleeding due to the rupture of a major blood vessel, penetration of the tumor through the intestinal wall, resulting in the spread of bacteria from the colon to the abdominal cavity, and fluid accumulation in the abdominal cavity.

These symptoms may not always be related to cancer; other health problems can cause similar symptoms. However, individuals experiencing any of these should seek medical attention for early diagnosis and treatment. Generally, there is no pain in the early stages of cancer. Consulting a doctor without waiting for pain to develop is important for early cancer diagnosis.

How is the diagnosis of colon cancer made?

Like other cancers, colon cancers may not present symptoms until they grow significantly. Therefore, the goal should be to identify the tumor before symptoms of cancer appear. Screening a person for cancer before symptoms develop helps in the early detection of polyps and cancer. Early recognition and removal of polyps can prevent colorectal cancer. When diagnosed early, the treatment of colorectal cancer can be more effective. For this reason, individuals over the age of 50 should be monitored, and those at increased risk for colorectal cancer should be placed in screening programs earlier.

Screening tests used for early diagnosis include:

• Fecal occult blood test: Since cancers and polyps bleed, this test can detect small amounts of blood in the stool. However, non-cancerous bleeding causes such as hemorrhoids can also result in a positive test. If the fecal occult blood test, performed correctly, is positive, an endoscopic examination of the colon is required.
• Sigmoidoscopy: The last 60 cm of the rectum and sigmoid colon are visualized. If polyps are detected, they can be removed through a procedure called polypectomy.
• Colonoscopy: The inner wall of the entire colon is visualized, and any existing polyps can be removed.
• Digital rectal examination: The doctor examines the rectum with a gloved finger lubricated with petroleum jelly.
• Double-contrast barium enema: This involves administering a white opaque substance rectally and then taking X-ray films to visualize the tumor. It is useful for showing large tumors but is not as reliable as a colonoscopy

How is screening for colorectal cancer performed?

For patients who do not fall into high-risk groups, starting at age 50, it is recommended to have fecal occult blood screening. For those over 50, at least a sigmoidoscopy every five years and a colonoscopy every ten years is suggested. In some countries, the screening age for colon cancer has been lowered to 45.

For patients in high-risk groups; those who have previously had polyps removed should have another colonoscopy within 1-3 years after the procedure. Individuals with a family history of colon cancer in close relatives such as parents should start screening at least 8-10 years before the age their relative was diagnosed or at age 40, whichever comes first.

Genetic testing should be performed for hereditary non-polyposis colorectal cancer. Individuals with familial adenomatous polyposis (FAP) should receive genetic counseling and be monitored with colonoscopy starting from age 10-15. Individuals with breast or female genital organ cancers should have periodic colonoscopies after age 40, and those with ulcerative colitis should have them periodically after diagnosis.

For individuals with symptoms and signs of colorectal cancer, it is necessary to determine whether these are due to cancer or another cause. If an abnormal finding (such as a polyp) is detected during examinations, a biopsy is essential 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?

The main treatment methods for colon cancer are surgery, radiation, and chemotherapy. The treatment varies depending on the location and stage of the tumor. Before starting treatment, patients can inquire about the stage of the disease, treatment options, side effects, negative impacts on their normal lives, treatment costs, and the existence of suitable new clinical trials.

• Surgery: Surgical treatment forms the mainstay in the treatment of cancer. For this, however, the cancer must not have spread to distant organs (such as the liver, lungs, brain, bones, etc.). In surgical methods, the tumor is removed along with the surrounding healthy tissue. Additionally, the tissue that connects the intestines to the body, called the mesentery, and lymph nodes are also removed. In rectal cancers, the tumor is removed along with a portion of the left side of the colon, and the two ends are connected. In cases where connection is not possible, the surgeon brings the end of the healthy colon out to the abdominal wall, closing the other end. This is called a colostomy. Stool is expelled through special colostomy bags. In most cases, this situation is temporary; once the colon or rectum heals after surgery, it is closed. For patients with tumors in the lower regions of the rectum, very close to the anus, colostomy may be permanent. In recent years, especially in cases of bowel tumors that have spread to the liver and lungs, surgical treatment has been applied even when the tumor in that area is completely removed, yielding very favorable results.
• Chemotherapy: Chemotherapy involves the use of anti-cancer drugs to kill cancer cells. It is referred to as systemic therapy because the drugs enter the bloodstream to kill cancer cells throughout the body. It is commonly used in certain stages of colon cancer and when the cancer has metastasized to other parts of the body. Anti-cancer drugs can be administered orally or through intravenous infusion. Patients can receive this treatment as outpatients in the hospital or occasionally as inpatients. Patients may receive chemotherapy alone or in combination with surgery and radiation therapy.
• Radiation Therapy: Also known as radiotherapy, this is a localized treatment that causes damage to tumor cells using ionizing radiation. The goal is to kill cancer cells in the treated area with high-energy rays. Radiation therapy can be given before surgery to shrink the tumor or after surgery to prevent recurrences, often in combination with chemotherapy. It is generally used for rectal cancers and some of their stages.