What is colon (colorectal) cancer?
The colon is part of your digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body). Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancers affecting either of these organs may also be called colorectal cancer. Colorectal cancers arise from the lining of the large intestine. When cancer arises from the lining of an organ like the large intestine, it is called a carcinoma.
What are the symptoms?
Most cases of colon cancer have no symptoms. The following symptoms, however, may indicate colon cancer:
- A change in bowel habits
- Diarrhea, constipation, or feeling that the bowel does not empty completely
- Blood (either bright red or very dark) in the stool
- Stools that are narrower than usual
- General abdominal discomfort (frequent gas pains, bloating, fullness, and/or cramps)
- Weight loss with no known reason
- Constant fatigue
- These symptoms may be caused by colon cancer or by other conditions. It is important to check with a doctor
The exact causes of colorectal cancer are not known. However, studies show that the following risk factors increase a person's chances of developing colorectal cancer:
- Age. Colon cancer is more likely to occur as people get older. This disease is more common in people over the age of 50 (45 for African Americans). However, colon cancer can occur at younger ages, even, in rare cases, in teenage years.
- Diet. Colon cancer seems to be associated with diets that are high in fat and calories and low in fiber. Researchers are exploring how these and other dietary factors play a role in the development of colorectal cancer.
- Polyps. Polyps are benign growths on the inner wall of the colon and rectum. They are fairly common in people over age 50. Some types of polyps increase a person's risk of developing colorectal cancer.
- Familial polyposis. A rare, inherited condition that causes hundreds of polyps to form in the colon and rectum. Unless this condition is treated, familial polyposis is almost certain to lead to colorectal cancer.
- Medical history. Research shows that women with a history of cancer of the ovary, uterus, or breast have a somewhat increased chance of developing colon cancer. Also, a person who has already had colon cancer may develop this disease a second time.
- Family history. First-degree relatives (parents, siblings, children) of a person who has had colon cancer are somewhat more likely to develop this type of cancer themselves, especially if the relative had the cancer at a young age. If many family members have had colon cancer, the chances increase even more.
- Ulcerative colitis. Ulcerative colitis is a condition in which the lining of the colon becomes inflamed. Having this condition increases a person's chance of developing colon cancer.
What are the stages of colon cancer?
If the diagnosis is cancer, the doctor needs to determine the stage (or extent) of disease. Staging is a careful attempt to find out whether the cancer has spread and, if so, to what parts of the body. Knowing the stage of the disease helps the doctor plan treatment. Listed below are descriptions of the various stages of colorectal cancer.
- Stage 0. The cancer is very early. It is found only in the innermost lining of the colon or rectum.
- Stage I. The cancer involves more of the inner wall of the colon or rectum.
- Stage II. The cancer has spread outside the colon or rectum to nearby tissue, but not to the lymph nodes.
(Lymph nodes are small, bean-shaped structures that are part of the body's immune system.)
- Stage III. The cancer has spread to nearby lymph nodes, but not to other parts of the body.
- Stage IV. The cancer has spread to other parts of the body. Colorectal cancer tends to spread to the liver and/or lungs.
- Recurrent. Recurrent cancer means the cancer has come back after treatment. The disease may recur in the colon, rectum, or in another part of the body.
How is it diagnosed?
The doctor will evaluate your medical history, perform a physical exam, and may order one or more diagnostic tests:
- Fecal occult blood test. A test to check stool (solid waste) for blood that can only be seen with a microscope. Small samples of stool are placed on special cards and returned to the doctor or laboratory for testing.
- Digital rectal exam. An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the rectum to feel for lumps or abnormal areas.
- Barium enema. A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the lower gastrointestinal tract and x-rays are taken. This procedure is also called a lower GI series.
- Sigmoidoscopy. A procedure to look inside the rectum and sigmoid (lower) colon for polyps, abnormal areas, or cancer. A sigmoidoscope (a thin, lighted tube) is inserted through the rectum into the sigmoid colon.
- Polyps or tissue samples may be taken for biopsy. Colonoscopy. A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope (a thin, lighted tube) is inserted through the rectum into the colon. Polyps or tissue samples may be taken for biopsy.
- Virtual Colonoscopy (VC). Virtual colonoscopy is the latest screening technology for diagnosing colon and bowel disease. VC uses x-rays and computers to produce two- and three-dimensional images of the colon (large intestine) from the lowest part, the rectum, all the way to the lower end of the small intestine and display them on a screen. VC can be performed with computed tomography (CT), sometimes called a CAT scan, or with magnetic resonance imaging (MRI).
- Biopsy. The removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer.
How is it treated?
Treatment depends on the size, location, and extent of the tumor, and on the patient's general health. Patients are often treated by a team of specialists that may include a gastroenterologist, surgeon, medical oncologist, and radiation oncologist. Several different types of treatment are used to treat colorectal cancer. Sometimes different treatments are combined.
- Surgery. Most common treatment for colorectal cancer. Generally, the surgeon removes the tumor along with part of the healthy colon or rectum and nearby lymph nodes. In most cases, the doctor is able to reconnect the healthy portions of the colon or rectum. When the surgeon cannot reconnect the healthy portions, a temporary or permanent colostomy is necessary. Colostomy, a surgical opening (stoma) through the wall of the abdomen into the colon, provides a new path for waste material to leave the body. After a colostomy, the patient wears a special bag to collect body waste. Some patients need a temporary colostomy to allow the lower colon or rectum to heal after surgery. About 15 percent of colorectal cancer patients require a permanent colostomy.
- Chemotherapy. Anticancer drugs to kill cancer cells. Some anticancer drugs are given in the form of a pill. Chemotherapy may be given to destroy any cancerous cells that may remain in the body after surgery, to control tumor growth, or to relieve symptoms of the disease. Chemotherapy is a systemic therapy, meaning that the drugs enter the bloodstream and travel through the body. Most anticancer drugs are given by injection directly into a vein (IV) or by means of a catheter, a thin tube that is placed into a large vein and remains there as long as it is needed. Some anticancer drugs are given in the form of a pill.
- Radiation therapy. High-energy x-rays to kill cancer cells. Radiation therapy is a local therapy, meaning that it affects the cancer cells only in the treated area. Most often it is used in patients whose cancer is in the rectum. Doctors may use radiation therapy before surgery (to shrink a tumor so that it is easier to remove) or after surgery (to destroy any cancer cells that remain in the treated area). Radiation therapy is also used to relieve symptoms. The radiation may come from a machine (external radiation) or from an implant (a small container of radioactive material) placed directly into or near the tumor (internal radiation). Some patients have both kinds of radiation therapy.
- Biological therapy. Also called immunotherapy, uses the body's immune system to fight cancer. The immune system finds cancer cells in the body and works to destroy them. Biological therapies are used to repair, stimulate, or enhance the immune system's natural anticancer function. Biological therapy may be given after surgery, either alone or in combination with chemotherapy or radiation treatment. Most biological treatments are given by injection into a vein (IV).
Why should I be concerned?
You can prevent colon cancer with early screening. Together, cancers of the colon and rectum are among the most common cancers in the United States. They occur in both men and women and are most often found among people who are over the age of 50. Yet most people over the age of 50 (45 for African Americans) have yet to be screened, partly due to the method used. Over 148,000 cases of colorectal cancer are expected to be diagnosed in the United States this year. Second only to lung cancer for cancer related deaths in the United States, colorectal cancer is expected to claim the lives of 50,000 in year 2008.