Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon. In other words Colon cancer is cancer of the large intestine or colon, the lower part of the digestive system.
Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become cancerous.
Polyps may be small and produce few, if any, symptoms, so it’s important to get regular screening tests to help prevent colon cancer. If signs and symptoms of cancer do appear, they may include a change in bowel habits, blood in the stool, persistent cramping, gas or abdominal pain.
Despite the relatively high number of cases and deaths due to colon cancer, screening tests, along with a few simple changes in the diet and lifestyle, can dramatically reduce the overall risk of developing colon cancer.
Colon Cancer Causes
Cancer forms malignant cells in the tissues of various parts of the body depending on the type of cancer. Cancer affects the cells, the basic units of life. Healthy cells grow and divide in an orderly way but sometimes this growth gets out of control and cells continue to divide in an abnormal manner.
In the colon and rectum, this exaggerated growth may cause precancerous polyps (adenomas, or adenomatous polyps) to form in the lining of the intestine.
Over a long period of time some of these polyps may become cancerous. In later stages of the disease, cancerous polyps may penetrate the colon walls and spread (metastasize) to nearby lymph nodes and other organs.
Polyps can occur anywhere in the large intestine, the muscular tube that forms the last part of the gastrointestinal tract. Polyps are either mushroom-shaped or flat and may be large or small. There are also several different types of colon polyps. Among the most common colon cancer causes are:
- Adenomas: This type of polyps has the potential to become cancerous and is usually removed during screening tests such as flexible sigmoidoscopy or colonoscopy.
- Hyperplastic polyps: These types of polyps are very rare if ever occur form a risk factor for colon cancer.
- Inflammatory polyps: These polyps may follow a bout of ulcerative colitis. Some inflammatory polyps may become cancerous, so having ulcerative colitis increases the overall risk of colon cancer
Colon Cancer Stage
After colon cancer has been diagnosed, tests are done to find out if cancer cells have spread within the colon or to other parts of the body. This process is called Staging.
The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. Colon cancer has four distinct stages, along with a fifth stage that is called ‘recurring‘. Each colon cancer stage has different treatment options
This is the earliest stage of colon cancer. The cancer only involves the lining, or mucosa, of the colon is confined to polyp(s).
Stage I colon cancer involves more than just the inner lining of the colon. The polyp has progressed to a tumor, and extends into the wall of the colon.
Stage II colon cancer is when the cancer has spread beyond the colon to the tissue that surrounds the colon but has not spread to lymph nodes. Cancer spreading in this manner from one part of the body to another is called metastasis.
When the cancer spread outside the colon and on to the lymph nodes in the area surrounding the colon is known as Stage III colon cancer In this stage, the cancer has not spread to other organs in the body, and treatment is more aggressive.
In this stage IV colon cancer, the cancer had spread to other organs in the body such as the lungs or liver.
Cancer that comes back again after treatment, either in the colon, or in some other part of the body, is called recurrent.
Colon Cancer Symptoms or Colon Cancer Signs
Many people with colon cancer may have no symptoms in the early stages of the disease. When symptoms appear, they’ll likely vary, depending on the cancer’s size and location in the large intestine. In some cases, the symptoms may result from a condition other than cancer, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and sometimes diverticulosis or diverticulitis. Like colon cancer, these conditions are treatable.
Following are the colon cancer symptoms or colon cancer signs:
- A change in the bowel habits, including diarrhea or constipation or a change in the consistency of the stool for more than a couple of weeks
- Narrow stools
- A feeling that the bowel doesn’t empty completely
- Rectal bleeding or blood in the stool
- Persistent abdominal pain or discomfort, such as cramps, gas
- Abdominal pain with a bowel movement
- Unexplained and unintentional weight loss
Blood in the stool may be a sign of cancer, but it can also indicate other conditions.
Colon Cancer Treatment
There are different types of colon cancer treatment methods for patients with the disease.
Some treatments are standard (the currently used treatment), and some are being tested in clinical trials.
Three types of standard treatment are used. These include the following:
Surgery (removing the cancer in an operation) is the most common treatment for all stages of colon cancer. A doctor may remove the cancer using one of the following types of surgery:
- Local excision: If the colon cancer is found at a very early stage, the doctor may remove it without cutting through the abdominal wall. Instead, the doctor may put a tube through the rectum into the colon and cut the cancer out. This is called a local excision. If the colon cancer is found in a polyp (a small bulging piece of tissue), the operation is called a polypectomy.
- Resection: This type of surgery is performed when the colon cancer is larger. A partial colectomy (removing the cancer and a small amount of healthy tissue around it) is done. The doctor may then perform an anastomosis (sewing the healthy parts of the colon together). The doctor will also usually remove lymph nodes near the colon and examine them under a microscope to see whether they contain cancer.
- Resection and colostomy: If the doctor is not able to sew the 2 ends of the colon back together, a stoma (an opening) is made on the outside of the body for waste to pass through. This procedure is called a colostomy. A bag is placed around the stoma to collect the waste. Sometimes the colostomy is needed only until the lower colon has healed, and then it can be reversed. If the doctor needs to remove the entire lower colon, however, the colostomy may be permanent.
- Radiofrequency ablation: The use of a special probe with tiny electrodes that kill colon cancer cells. Sometimes the probe is inserted directly through the skin and only local anesthesia is needed. In other cases, the probe is inserted through an incision in the abdomen. This is done in the hospital with general anesthesia.
- Cryosurgery: A treatment that uses an instrument to freeze and destroy abnormal tissue, such as carcinoma in situ. This type of treatment is also called cryotherapy.
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells after surgery, to shrink large tumors before an operation so that they can be removed more easily, or to relieve symptoms of colon cancer and rectal cancer.
There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the colon cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
The goal of therapy is to damage the tumor without harming the surrounding tissue. If the cancer has spread through the wall of the rectum, the doctor may recommend radiation treatments in combination with chemotherapy after surgery. This may help prevent colon cancer from reappearing in the same place.
Side effects of radiation therapy may include diarrhea, rectal bleeding, fatigue, loss of appetite and nausea.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. Chemotherapy can be used to destroy cancer cells after surgery, to control tumor growth or to relieve symptoms of colon cancer.
The doctor may recommend chemotherapy if the colon cancer has spread beyond the wall of the colon. In some cases, chemotherapy is used along with radiation therapy. The way the chemotherapy is given depends on the type and stage of the colon cancer being treated.
When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy).
Possible side effects of chemotherapy include nausea and vomiting, mouth sores, fatigue, hair loss and diarrhea.
Chemoembolization of the hepatic artery may be used to treat cancer that has spread to the liver. This involves blocking the hepatic artery (the main artery that supplies blood to the liver) and injecting anticancer drugs between the blockage and the liver. The liver’s arteries then deliver the drugs throughout the liver. Only a small amount of the drug reaches other parts of the body. The blockage may be temporary or permanent, depending on what is used to block the artery. The liver continues to receive some blood from the hepatic portal vein, which carries blood from the stomach and intestine.
Biologic therapy is a treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or immunotherapy.
Colon Cancer Prognosis
Prognosis is a chance of recovery. Certain factors affect prognosis and treatment options.
The colon cancer prognosis (chance of recovery) depends on the following:
- Colon cancer prognosis mostly depends on the stage of the cancer (whether the cancer is in the inner lining of the colon only, involves the whole colon, or has spread to other places in the body).
- Whether the cancer has blocked or created a hole in the colon.
- The blood levels of carcinoembryonic antigen (CEA; a substance in the blood that may be increased when cancer is present) before treatment begins.
- Whether the cancer has recurred.
- The patient’s general health.
If the patient’s colon cancer does not come back or recur within 5 years, then it is considered to be cured. This is because colon cancer rarely comes back after 5 years.
Stage I, II, and III cancers are considered potentially curable. In most cases, stage IV cancer is not curable.
Stage I has a 90% 5-year survival.
Stage II has a 75-85% 5-year survival, and Stage III a 40-60% 5-year survival.
These numbers take into account that for stage III patients (and in some studies, stage II patients) chemotherapy improves the chance of 5-year survival.
Patients with stage IV disease rarely live beyond five years and the median survival (meaning half the patients live longer, and half shorter) with treatment is between 1 and 2 years.
Cancer Colon Prevention
The most encouraging news about colon cancer and rectal cancer is that one can actually reduce the risk by having regular screenings. That’s because with regular screening, one can have polyps removed before they have a chance to turn into colon cancer. Few simple changes in the diet and lifestyle reduce the risk. The following suggestions may help for a better living and colon cancer prevention:
- Eat plenty of fruits, vegetables and whole grains.
- Limit fat, especially saturated fat.
- Taking vitamins and minerals in required quantity. Calcium, magnesium, pyridoxine (vitamin B-6) and vitamin B-9 may help reduce the risk of colon cancer.
- Eating foods rich in calcium and folic acid
- Limit alcohol consumption.
- Quit smoking.
- Maintain a healthy body weight and stay physically active.