What Is It?
Colorectal cancer is a type of uncontrolled growth of abnormal cells that can develop in the colon, rectum or both. Together the colon and rectum make up the large intestine (large bowel). It carries the remnants of digested food from the small intestine and eliminates them as waste through the anus.
Colorectal tumors begin as polyps (small growths) on the inside of the large intestine. Polyps that aren’t removed eventually can become cancerous, penetrate through the wall of the colon or rectum, and spread to other areas.
Colorectal cancer is a common type of cancer in the United States. It is the second most common cause of death from cancer in the country. The American Cancer Society estimates that 146,940 new cases of colorectal cancer will be diagnosed in 2004, and about 56,730 people in the United States will die of this disease. The older you get, the more likely you are to develop colorectal cancer.
Factors that increase the risk of developing colorectal cancer include:
- Family history — Heredity may play a role in up to 10 percent of all cases of colorectal cancer. Genetic defects have been linked to a number of cancer syndromes that run in families and make family members more likely to develop polyps and colorectal cancer.
- A personal history of the disease — A personal history increases the risk of developing colorectal cancer again.
- A personal history of adenomatous polyps — A personal history of polyps also increases the risk.
- Inflammatory bowel disease (chronic ulcerative colitis, Crohn’s disease) — The longer and more severely the colon is inflamed, the greater the risk of cancer.
- Poor diet — Diets low in fiber and high in fat, especially saturated fat, may increase the risk of colorectal cancer.
- A sedentary lifestyle — Among people who exercise regularly, the risk of colon cancer is reduced by half. Even regular brisk walking may reduce a person’s risk of developing colon cancer.
- Race and ethnicity — Different racial and ethnic groups in the United States have very different rates of colorectal cancer. Alaska natives are most likely to develop the disease while Hispanics and Filipinos are the least likely. Whites and African-Americans fall near the middle.
Precancerous polyps and early colorectal cancer generally don’t cause symptoms. More advanced cancer can cause any of the following symptoms.
- A change in bowel habits
- Diarrhea or constipation
- Blood in the stool (bright red, black or very dark)
- Narrowed stools (about the thickness of a pencil)
- Bloating, fullness or stomach cramps
- Frequent gas pains
- A feeling that the bowel does not empty completely
- Weight loss without dieting
- Continuing fatigue
Colorectal cancer usually is diagnosed by a sigmoidoscopy or colonoscopy. In these tests, a flexible viewing tube is inserted into your rectum and colon to look for polyps or cancerous masses. You also may have a test called a barium enema. In this test, a fluid containing a substance called barium is pumped into your rectum before X-rays are taken. The barium helps abnormalities show up on the X-rays. These tests provide information about the size and location of the cancer.
Sometimes, if the cancer has spread outside the colon or rectum, you may need a biopsy of that area. In a biopsy, a small piece of tissue is removed and examined in a laboratory.
Other tests also may be needed, including:
- An abdominal Computed tomography scan can provide further information.
- An endorectal Ultrasound scan can be useful with cancer of the rectum.
- A complete physical examination and a chest X-ray will be done after the cancer is diagnosed to see if it has spread.
- Blood tests will measure levels of a substance called carcinoembryonic antigen, which sometimes is higher than normal in people with colorectal cancer. Blood tests also can check how well your liver is functioning, as colon cancer frequently spreads to the liver.
Without treatment, colon cancer will continue to grow.
The best defense against colorectal cancer is regular screening. Screening tests are designed to find benign polyps (precancerous growths) that can be removed before they become cancerous (malignant) and catch cancer at an early stage when it is easier to cure. The American Cancer Society recommends that all adults begin screening for colorectal cancer at age 50. People at higher risk should begin screening earlier. Recommended screening methods include:
- Digital rectal examination — Beginning at age 40, then yearly after 50; should not be used as the only screening method
- Fecal occult blood test — Yearly beginning at age 50
- Sigmoidoscopy — Every five years beginning at age 50, unless you have a colonoscopy
- Colonoscopy — As a routine screening test every 10 years, beginning at age 50, unless you have a screening sigmoidoscopy every five years
- Double-contrast barium enema — Not the preferred method of routine screening, but can be performed instead of colonoscopy or in addition to sigmoidoscopy every five years
In addition to these screening tests, other methods can reduce a person’s risk of developing colon cancer. Daily exercise and a diet low in fats, especially saturated fats, and high in fruits, vegetables and whole-grain foods may lower your risk of colorectal cancer. Also, some scientific studies have suggested that taking aspirin or folate every day may reduce a person’s risk of colon cancer. These should be discussed with your doctor to see if they are appropriate for you.
Surgery is the primary method of treating colorectal cancer. Surgery sometimes is followed with chemotherapy or radiation. The extent of surgery and whether you need treatment after surgery depends on the stage of the disease and whether it is in the colon or rectum.
There are three slightly different systems for staging colon cancer: Dukes, Astler-Coller and AJC/TNM. Following are the stages in the AJC/TNM system and recommendations for treatment in addition to surgery.
- Stage 0 — Cancer is confined to the inner layer of the colon or the rectal lining. No treatment is recommended after surgery to remove polyps or cancer.
- Stage I — Cancer has grown through the inner rectal wall or the inner lining of the colon and underlying layers but has not penetrated the colon wall. Usually, no treatment is recommended after surgery.
- Stage II — Cancer has grown completely through the colon or rectal wall but hasn’t spread to nearby lymph nodes. Chemotherapy may be done after surgery in some cases of colon cancer. For rectal cancer, chemotherapy and radiation can be done before or after surgery.
- Stage III — Cancer has spread to nearby lymph nodes but not to other parts of the body. For colon cancer, chemotherapy typically is recommended after surgery. For rectal cancer, chemotherapy and radiation usually are given either before or after surgery.
- Stage IV — Cancer has spread to distant organs, most commonly the liver or lungs. Treatment after surgery consists of chemotherapy, radiation therapy or both to relieve symptoms of advanced cancer and, in rectal cancer, to prevent blockage of the rectum. Occasionally, surgery is done to remove cancer from the sites where it has spread.
For colon cancer, surgery removes the cancerous area of the colon with some surrounding normal tissue and nearby lymph nodes. The severed ends of the colon are reconnected so that the colon can function normally. Occasionally, very early cancers can be removed through colonoscopy. People who have had colon cancer surgery usually do not need a colostomy, in which a hole is made in the abdomen, and the colon is rerouted through the hole to rid the body of stool. This procedure may be done temporarily if emergency surgery is done to remove a cancerous area. Recuperation time varies depending on several factors, including the person’s age and general health and the extent of the surgery.
For rectal cancer, treatment often combines surgery with chemotherapy and radiation, depending on the stage of the disease. Chemotherapy and radiation can be given before or after surgery.
Surgical procedures used for rectal cancer, depending on the location and stage of the cancer, include:
- Polypectomy — This procedure removes polyps containing stage 0 tumors.
- Local excision — This procedure removes superficial cancers and some nearby tissue from the rectum’s inner layer, often working through the anal canal.
- Low anterior resection — This procedure is used for most rectal cancers, except when the tumor is very close to the anal sphincter. The colon and rectum are reconnected, and the anus is spared.
- Abdominoperineal resection — This surgery treats cancer in the lowest part of the rectum. Once the cancerous area is removed, a colostomy is done to allow wastes to drain through an opening in the abdominal wall.
- Pelvic exenteration — This surgery removes the rectum, bladder, prostate, uterus and other nearby organs if cancer has spread to them. A colostomy and drainage for urine are needed. This type of aggressive surgery is rarely needed.
When To Call A Professional
Visit a doctor for regular screenings according to the guidelines. Also, see your doctor if you have any of the signs or symptoms of colorectal cancer.
The outlook for colorectal cancer depends on the stage of the disease. The percent of people who survive five years or more range from near 100 percent for stage 0 disease to about 5 percent for stage IV disease.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.