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Colorectal Cancer

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 (also called the large bowel). The large intestine carries the remnants of digested food from the small intestine and eliminates them as waste through the anus.

Colorectal tumors begin as small growths (polyps) on the inside of the large intestine. Polyps that aren't removed eventually can become cancerous, break 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 about 145,000 new cases of colorectal cancer are diagnosed each year, and about 56,000 people in the United States die of this disease each year.

Risk Factors

The older you get, the more likely you are to develop colorectal cancer. Other factors that increase the risk of developing colorectal cancer include:

  • Family history Heredity may play a role in up to 10% of all cases of colorectal cancer. Genetic defects have been linked to a number of cancer syndromes that run in families. These make family members more likely to develop polyps and colorectal cancer.

  • A personal history of the disease If you have been diagnosed with colorectal cancer once, you are more likely to develop the disease again.

  • A personal history of adenomatous polyps If you once had polyps, this increases your risk of colorectal cancer.

  • 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 somewhere in between.


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 (more often, less often, a feeling that the bowel does not empty completely)

  • 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


Doctors usually diagnose colorectal cancer using a sigmoidoscopy or colonoscopy. In these tests, a doctor inserts a flexible viewing tube into your rectum and colon to look for polyps or cancerous masses. You may have a test called a barium enema, in which a fluid containing a substance called barium is pumped into your rectum and then 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 doctor or surgeon removes a small piece of tissue that is examined in a laboratory.

Other possible tests include:

  • An abdominal computed tomography (CT) scan

  • An endorectal ultrasound scan with cancer of the rectum.

  • A complete physical examination and a chest X-ray after the cancer is diagnosed to see if it has spread.

  • Blood tests to 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 because colon cancer often spreads to the liver.

Expected Duration

Without treatment, colon cancer will continue to grow.


The best defense against the spread of colorectal cancer is regular screening. Screening tests are designed to find precancerous growths (benign polyps) so they can be removed before they become cancerous (malignant). 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; do not use 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 it can be used instead of colonoscopy or in addition to sigmoidoscopy every five years

  • Virtual colonoscopy More accurate X-ray pictures of the colon using CT scanning technology. This is a possible alternative to other methods of screening.

To reduce your risk of developing colon cancer, consider the following. Daily exercise and a diet low in fats, especially saturated fats may lower your risk of colorectal cancer. Also, some studies suggest that taking aspirin or folate every day may reduce a person's risk of colon cancer. Talk to your doctor to see if they are appropriate for you.


Surgery is the primary method of treating colorectal cancer. After surgery, you may have 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 categorizing colon cancer: Dukes, Astler-Coller and AJC/TNM. Here are the stages in the AJC/TNM system, aloing with 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 the underlying layers, but has not broken through the colon wall. Usually, no treatment is recommended after surgery.

  • Stage II Cancer has grown completely through the colon or rectal wall but it hasn't spread to nearby lymph nodes. Chemotherapy may be used after surgery in some cases of colon cancer. For rectal cancer, chemotherapy and radiation can be used 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 before or after surgery.

  • Stage IV Cancer has spread to distant organs, most commonly to the liver or lungs. Treatment after surgery consists of chemotherapy, radiation therapy or both to relieve the symptoms of advanced cancer and, in rectal cancer, to prevent the blockage of the rectum. Occasionally, surgery is needed to remove cancer from the sites where it has spread.

For colon cancer, surgery removes the cancerous area of the colon and some surrounding normal tissue and the nearby lymph nodes. The two 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 needed to remove a cancerous area. Recuperation time varies depending on several factors, including the person's age, 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 depend on the location and stage of the cancer. They 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 no colostomy is needed.

  • Abdominoperineal resection This surgery treats cancer in the lowest part of the rectum. Once the cancerous area is removed, a colostomy is needed 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 5 years or more range from near 100% for stage 0 to about 5% for stage IV.

Additional Info

American Cancer Society (ACS)

1599 Clifton Road, NE

Atlanta, GA 30329-4251

Toll-Free: 1-800-227-2345

Cancer Research Institute

681 Fifth Ave.

New York, NY 10022

Toll-Free: 1-800-992-2623


Centers for Disease Control and Prevention (CDC)

1600 Clifton Road

Atlanta, GA 30333

Phone: 404-639-3534

Toll-Free: 1-800-311-3435

National Cancer Institute (NCI)

U.S. National Institutes of Health

Public Inquiries Office

Building 31, Room 10A03

31 Center Drive, MSC 8322

Bethesda, MD 20892-2580

Phone: 301-435-3848

Toll-Free: 1-800-422-6237

TTY: 1-800-332-8615


Online Medical Reviewer: LeWine, Howard MD
Date Last Reviewed: 12/14/2005
Copyright by Harvard University. All rights reserved. Content Licensing by Belvoir Media Group
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