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Provides information on all forms of cancer and offers numerous brochures and publications for patients and healthcare professionals. Their colon cancer page helps users to answer critical questions about colon cancer.
This U.S. government site provides information on colon cancer treatment, screening, prevention, genetics, clinical trials and supportive care.
This U.S. Government site includes a section on colorectal cancer prevention and control initiatives, including information on their Screen for Life national campaign and a host of other resources and publications.
This site is hosted by a network of colon cancer survivors and their loved ones. Support groups, listserves, chat rooms, matching list that connects newly diagnosed with long term survivors, an extensive library of colorectal cancer and other relevant links, literature, awareness pins and t-shirts are all available.
The Colon Cancer Alliance (CCA) is an organization of colon and rectal cancer survivors, their families, caregivers, people genetically predisposed to the disease and the medical community. They offer a variety of support services in addition to educational material.
OncologySTAT is committed to providing up to date news, journal scans, chemotherapy regimens, interviews with reputable doctors and informative videos. OncologySTAT's mission is to improve worldwide cancer care and prevention by providing healthcare professionals with immediate integrated access to the most authoritative evidence-based information available.
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Colon cancer, colorectal cancer, and rectal cancer are different names for what essentially is the same disease. Colon cancer is the third most common type of cancer among American men and in women and is the third leading cause of cancer-related deaths (after lung cancer) in the United States. A few facts:

  • Most cases of colon cancer occur in men and women over the age of 50.
  • If the disease is diagnosed at an early stage, there is a good chance that it can be cured. In general, the more advanced the cancer is (the more it has grown and spread), the less chance there is that treatment will be successful. However, even in these cases, treatment can often slow the progress of the disease.
  • People over the age of 50, as well as those who are considered at high risk for colon cancer, should be screened on a routine basis so that the disease can be detected at an early stage. Get more facts about colon cancer

Colon Cancer and the Gastrointestinal System
Colorectal is a word that means 'the colon and rectum', which are parts of the gastrointestinal (GI) tract. The GI tract starts at the mouth and ends at the anus. When you eat or drink, the food and liquid travel down the esophagus into the stomach. The stomach churns up the food and then passes it into the small intestine.

The small intestine (sometimes called the small bowel), which can be up to 20 feet long, is where food is digested and absorbed. Undigested food, water, and waste products are then passed into the large intestine (sometimes called the large bowel). The main part of the large intestine is called the colon, which is about five feet long. This is split into four sections, the ascending, transverse, descending, and sigmoid colon. Some water and salts are absorbed into the body from the colon. The colon leads into the rectum, which is the last eight to 10 inches of the large intestine. The rectum stores stools before they are passed out of your body through the anus.

Cancer Defined
Cancer is a disease of the cells in the body.

The body is made up from millions of tiny cells. There are many different types of cells in the body, and there are many different types of cancer which can occur in different types of cells. What all types of cancer have in common is that the cancer cells are abnormal and multiply (grow) at an out-of-control rate.

A malignant tumor is a lump or growth of tissue made up from cancer cells which continue to multiply. Malignant tumors can invade and damage nearby tissues and organs.

Malignant tumors may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumor and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form 'secondary tumors (metastases) in one or more parts of the body. These secondary tumors may then grow, invade and damage nearby tissues and organs, and spread again.
Some cancers are more serious than others, some are more easily treated than others (particularly if diagnosed at an early stage), and some have a better outlook (prognosis) than others.

Cancer is not just one condition. If you are diagnosed with cancer, it's important to know exactly what type of cancer has developed, how large it has become, and whether it has spread. This will enable you to get reliable information on your treatment options and prognosis.

Colorectal Cancer
Colorectal cancer is a cancer of the large intestine. It is sometimes called colon cancer or bowel cancer. It is one of the most common cancers in the United States. Colorectal cancer can affect any part of the large intestine, but it most commonly first develops in the lower part of the descending colon, the sigmoid colon, or rectum.

In most cases, colorectal cancer develops from a polyp which has formed on the lining of the large intestine.  Sometimes colorectal cancer begins from a cell within the lining of the large intestine which becomes cancerous.

As the cancer cells multiply they form a tumor, which can invades deeper into the wall of the intestine. Some cancerous cells may break off into the lymph channels or bloodstream. The cancer may then spread (metastasize) to nearby lymph nodes or to other areas of the body – most commonly the liver and lungs.

Polyps and Colorectal Cancer
A bowel polyp (adenoma) is a small growth which sometimes forms on the inside lining of the intestine. Most bowel polyps develop in older people. Polyps are benign (non-cancerous) and usually cause no problems.

Sometimes, however, a benign polyp can turn cancerous. If this happens, the change usually takes place after a number of years. Most colorectal cancers develop from a polyp which has been present in the large intestine for anywhere from five to 15 years.

Causes of Colorectal Cancer
A cancerous tumor starts from one abnormal cell. In the case of colorectal cancer, it is a cell in a polyp which is the most common site for a cancerous cell to develop. While the exact reason why a cell becomes cancerous is unknown, researchers believe the change occurs when something damages or alters certain genes in the cell. This makes the cell abnormal and multiply in an out-of-control fashion.

Risk Factors
Although colorectal cancer can develop for no apparent reason, there are certain risk factors which can increase the chance that colorectal cancer will develop. These include:

  • Aging – colorectal cancer is more common in older people. Most cases are in people over the age of 50. 
  • Heredity – if a close relative has had colorectal cancer, you may be at increased risk for the disease.
  • Other conditions:
    • If you have familial adenomatous polyposis or hereditary non-polyposis colorectal cancer. (These are inherited disorders.)
    • If you have ulcerative colitis (a condition of the colon) for more than eight to 10 years.
  • Obesity.
  • Lifestyle factors: lack of exercise; low intake of fruits and vegetables and high intake of red meat; high alcohol consumption; and smoking.

Preventive Factors
There is a reduced risk of developing colorectal cancer in: 

  • Women who take hormone replacement therapy (HRT).
  • People who eat a lot of fruit and vegetables.
  • People who take anti-inflammatory medicines (such as aspirin) for other conditions.

Symptoms of Colorectal Cancer
When colorectal cancer first develops and is small, it usually causes no symptoms. As it grows, the symptoms which develop can vary, depending on the site of the tumor. The most common symptoms are:

  • Bleeding from the tumor. You may see blood mixed up with your feces (stools or diarrhea). Sometimes the blood can make the feces turn a very dark color. The bleeding is not usually severe and in many cases the bleeding is not noticed because only a small amount of blood is mixed with the feces. However, small amounts of bleeding which occur regularly can lead to anemia which can make you tired and pale.
  • Passing mucus with the feces.
  • Changes from your usual bowel movements. This means you may pass feces more or less often than usual.
  • Bouts of diarrhea or constipation.
  • A feeling of not fully emptying the rectum after a bowel movement.
  • Abdominal pains.

Growth and Spread of Tumors
As a tumor grows in the intestine, symptoms may become worse and can include:

  • The same symptoms as above, but more severe.
  • You may feel generally unwell, tired, or lose weight.
  • If the cancer becomes very large, it can cause a blockage (obstruction) of the intestine. This causes severe abdominal pain and other symptoms such as vomiting.
  • Sometimes the cancer makes a hole in the wall of the intestine (perforation). If this occurs, feces can leak into the abdomen.

All the above symptoms can also be caused by other conditions, so tests are needed to determine whether or not you have colorectal cancer. If colorectal cancer spreads to other parts of the body, various other symptoms can develop. 

Quick Facts

  • Colorectal cancer – cancer of the colon or rectum – is the third leading cause of cancer-related deaths (after lung cancer) in the United States and is the third most common type of cancer in men and in women.
  • In 2005, among Americans, an estimated 145,290 new cases of colorectal cancer will be diagnosed and an estimated 56,290 Americans will die from the disease.
  • Reducing the number of deaths from colorectal cancer depends on detecting and removing precancerous colorectal polyps, as well as detecting and treating the cancer in its early stages. Colorectal cancer can be prevented by removing precancerous polyps or growths, which can be present in the colon for years before invasive cancer develops.
  • It's estimated that if everybody age 50 or older had regular screening tests, at least one-third of deaths from this cancer could be avoided.
  • The risk of developing colorectal cancer increases with advancing age. More than 90% of cases occur in people who are 50 or older. Other risk factors include:
    • Inflammatory bowel disease
    • A personal or family history of colorectal cancer or colorectal polyps
    • Certain hereditary syndromes
  • Lifestyle factors that may contribute to increased risk of colorectal cancer include:
    • Lack of regular physical activity
    • Low intake of fruits and vegetables
    • A low-fiber and high-fat diet
    • Obesity, alcohol consumption, and tobacco use

Get more facts about colorectal cancer from the American Cancer Society

*Quick Facts have been reviewed by Medical Advisors and are current as of October 2005.

Ask Your Doctor

This list questions will provide a good starting point for a discussion with your doctor.  However, it is not a complete list.

  • When should I be screened for colorectal cancer and how often?
  • Can a screening test determine if I have colorectal cancer?
  • What screening tests are used, and what are the pros and cons of each type of test?
  • Are colorectal cancer screening tests uncomfortable? What will I need to do to prepare for testing?
  • Who will perform the tests and interpret the results?
  • Are screening tests covered by insurance companies and Medicare?
  • Are screening tests worth the cost and discomfort?
  • If a screening test finds polyps, how will they be removed?
  • Are home screening tests for colorectal cancer accurate?
  • What can I do to prevent colorectal cancer?

Key Point 1

Screening for colon cancer can find cancer at an early curable stage and can prevent cancer by finding and removing polyps that might eventually turn into cancer.

Colorectal cancer is more common in older people, so doctors usually screen people 50 years of age and older.

Doctors generally advise screening at a younger age for people who have risk factors that make them more likely to get colorectal cancer. You should be screened for colorectal cancer before age 50 if you:

  • Have had colorectal cancer or large polyps in the past
  • Have a close relative (brother, sister, parent or child) who has had colorectal cancer before age 60
  • Have ulcerative colitis or Crohn's disease
  • Have a hereditary colon cancer syndrome, such as familial adenomatous polyposis or hereditary non-polyposis colorectal cancer.

If you are in a high-risk group for colorectal cancer, you may also need to be tested more often than someone who doesn't have risk factors.

Screening Tests for Colorectal Cancer
Several tests, which are generally accepted by members of the medical community, are available to screen for colorectal cancer. Some are used alone, while others are used in combination with each other. Your doctor can talk with you about which type of test is best for you. These tests include:

  • Fecal occult blood test (FOBT). This test checks for occult (hidden) blood in the stool. You receive a test kit from your doctor or health care provider. At home, you place a small amount of your stool from three bowel movements in a row on test cards. You return the cards to your doctor's office or a lab, where the stool samples are tested for hidden blood.
  • Flexible sigmoidoscopy. This test allows the doctor to examine the lining of your rectum and lower part of your colon using a thin, flexible, lighted tube called a sigmoidoscope. It is inserted into your rectum and lower part of the colon.  
  • Combination of FOBT and flexible sigmoidoscopy. Some experts recommend combining the two tests described above to increase the chance of finding polyps and cancers.
  • Colonoscopy. This test – considered by many medical professionals to be the "gold standard" of screening exams for colorectal cancer – is similar to flexible sigmoidoscopy except that it allows the doctor to examine the lining of your rectum and entire colon using a thin, flexible, lighted tube called a colonoscope. While you are under sedation, this tube is inserted into your rectum and colon to enable the doctor to find and remove most polyps and some cancers.
  • Double Contrast Barium Enema. This test allows the doctor to see an x-ray image of the rectum and entire colon. First you receive an enema with a liquid called barium that flows from a tube into the colon, followed by an air enema. The barium and air create an outline around your colon, allowing the doctor to see if abnormalities are present.
  • Other tests. Computerized tomography (CT or CAT) colonography (also referred to as "virtual colonoscopy") and fecal DNA tests are experimental screening tests that are still under development. CT colonography is offered in some health care settings, but you should be aware that it is still considered experimental and should be used only in the context of a clinical trial. These exams are not accepted as standard practice at the present time.  Learn more about experiment screening tests for colorectal cancer from the Cancer Research and Prevention Foundation.

Colorectal Cancer Screening Guidelines
The American Cancer Society, the American Academy of Family Physicians, and the American Gastroenterological Association all have similar guidelines for colorectal cancer screening. Each believes that any of the tests or combinations of tests listed above may be used (together with a digital rectal exam at each screening). For people who have no risk factors, colorectal screening should begin at 50 years of age and continue with:

  • Fecal occult blood testing every year
  • Flexible sigmoidoscopy every five years
  • Fecal occult blood testing every year plus flexible sigmoidoscopy every five years
  • Double-contrast barium enema every 5  years
  • Colonoscopy every 10 years

Your family physician can advise you on which screening tests you should have and how often you should be screened.


Key Point 2

There are different colon cancer screening tests that have advantages and disadvantages. None have proven to be better than colonoscopy, but they can be used as alternative screening techniques. Whether or not they replace colonoscopy is a discussion you need to have with your doctor.

If a doctor suspects that you may have colorectal cancer, he or she will examine you to look for a lump in your abdomen, anemia, or other warning signs of colon cancer. The examination will usually include a digital rectal examination. This is where a doctor inserts a gloved finger through your anus into your rectum to feel if there is a tumor in the lower part of the rectum. However, this particular exam is not very sensitive, and it may not detect cancer when the disease is in it's early stages. Therefore, your doctor may recommend additional testing using one or more of the screening methods for colorectal cancer outlined in Key Point 1 .

Pros and Cons of Different Types of Colorectal Exams

There are pros and cons associated with each of the various tests that are used to screen for colorectal cancer.  Talk with your doctor about which is best for you.

Fecal occult blood test

  • Pros
    • Not complex
    • Can be done at home
    • Noninvasive, low risk
    • Inexpensive*
  • Cons
    • Patient may have to avoid some foods and medicines before and until stool samples are collected
    • Patient may find the task disagreeable and not adhere to completing all tests
    • Better for identifying cancers than pre-cancerous polyps; however, blood must be present to identify a problem
    • If blood is found, follow-up testing is needed

Flexible sigmoidoscopy

  • Pros
    • Increases the chance of finding polyps and early cancers versus the fecal occult blood test
    • May be performed in a primary care doctor's office
    • Moderate cost*
  • Cons
    • Cannot examine entire colon
    • Patient will have to restrict diet and use laxatives and/or enemas to clean out the colon and rectum
    • Invasive with very slight risk of perforation, infection, bleeding
    • Patient may experience some discomfort during or after exam (sedation is rarely used for test)
    • If polyps or lesions are found, a follow-up procedure is needed

(Colonoscopy is usually recommended as a follow-up test if any of the other screening tests are abnormal.)

  • Pros
    • Full colon visualization
    • Doctor will be able to identify polyps, which also can be removed during the test so only one bowel preparation is necessary
    • Sedation is used so the patient doesn't experience discomfort during the test
  • Cons
    • Patient will have to restrict diet and use laxatives and/or enemas to clean out the colon and rectum
    • There are risks association with sedation
    • Invasive with slight risk of perforation, infection, bleeding
    • Patient may experience some discomfort after exam
    • Patient is advised not to drive or work on the day of the exam due to sedation
    • Most expensive*

Double Contrast Barium Enema

  • Pros
    • Provides full colon visualization
    • Fairly good percentage of polyps and cancers can be detected at approximately 50 to 80 percent of polyps less than 1 cm in size, 70 to 90 percent of polyps larger than 1 cm and 50 to 80 percent of stage I and II adenocarcinomas
    • Low risk
    • Less expensive than colonoscopy*
  • Cons
    • Before the test, your doctor will recommend that you restrict your diet and use laxatives and/or enemas to clean out your colon and rectum.
    • Patient may feel discomfort during or after exam.
    • If polyps or lesions are found, a follow-up procedure is needed
    • The efficacy of barium enema in preventing deaths from colorectal cancer has not been evaluated in a controlled trial.

*Note:  The cost of individual screening tests vary, but the cost of lifetime programs of screening and follow-up of abnormal test results are comparable per year of life saved (assuming that screening begins at the age of 50 years and is discontinued at the age of 85 years).


Key Point 3

Aside from colonoscopy and other colon cancer screening, healthy diet, and exercise are important steps in preventing colon cancer.

According to the American Cancer Society, eating healthy diet and getting plenty of exercise are vital steps you can take to prevent colorectal cancer (along with regular screening for the disease).  The organization's recommendations include:

1. Eat a variety of healthful foods, with an emphasis on plant sources.

  • Eat five or more servings of a variety of vegetables and fruits each day.
    • Include vegetables and fruits at every meal and for snacks.
    • Eat a variety of vegetables and fruits.
    • Limit French fries, snack chips, and other fried vegetable products.
    • Choose 100% juice if you drink fruit or vegetable juices.
  • Choose whole grains in preference to processed (refined) grains and sugars.
    • Choose whole grain rice, bread, pasta, and cereals.
    • Limit consumption of refined carbohydrates, including pastries, sweetened cereals, soft drinks, and sugars.
  • Limit consumption of red meats, especially those high in fat and those which are processed.
    • Choose fish, poultry, or beans as an alternative to beef, pork, or lamb.
    • When you eat meat, select lean cuts and have smaller portions.
    • Prepare meat by baking, broiling, or poaching rather than by frying or charbroiling.
  • Choose foods that help you maintain a healthy weight.
    • When you eat away from home, choose foods that are low in fat, calories, and sugar, and avoid large portion sizes.
    • Eat smaller portions of high-calorie foods. Be aware that "low-fat" or "nonfat" does not mean "low-calorie," and that low-fat cakes, cookies, and similar foods are often high in calories.
    • Substitute vegetables, fruits, and other low-calorie foods for calorie-dense foods such as French fries, cheeseburgers, pizza, ice cream, doughnuts, and other sweets.

2. Adopt a physically active lifestyle.

  • Adults: engage in at least moderate activity for 30 minutes or more on five or more days of the week; 45 minutes or more of moderate-to-vigorous activity on five or more days per week may further enhance reductions in the risk of breast and colon cancer.
  • Children and adolescents: engage in at least 60 minutes per day of moderate-to-vigorous physical activity for at least five days per week.

3. Maintain a healthy weight throughout life.

  • Balance caloric intake with physical activity.
  • Lose weight if currently overweight or obese.

4. If you drink alcoholic beverages, limit consumption.

The American Cancer Society provides additional information on preventing colon cancer on its website.

Medline Plus

Medline Description: 

Conduct an off-site search for Colon Cancer information from MedlinePlus.  These up-to-date search results are based on search terms specific to Second Opinion Key Points.

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