Colorectal Cancer Basics
- Colorectal cancer is the second-leading cause of cancer deaths in the U.S.
- Men and women are at equal risk of developing colorectal cancer.
- Early detection of colorectal cancer leads to easier treatments and higher survival rates.
- More than one-third of colorectal cancer deaths could be avoided if all eligible individuals participated in regular screening.
- Colorectal cancer screening is safe and effective.
The colon is an important organ in your body’s digestive system. The colon, also known as the large intestine, consists of a long, thick tube that:
- Absorbs water and minerals from digested food.
- Contains the rectum, which stores undigested solid waste.
Cancer of the colon and rectum, called colorectal cancer, occurs when a growth in the lining of the colon or rectum becomes malignant, or cancerous. It is the second-leading cause of cancer deaths in the U.S. However, if caught early, colorectal cancer can be cured. It’s important for you to understand your risks for colorectal cancer, the symptoms of colorectal cancer and screening tests that can detect cancerous growths. With simple preventive steps, you can also reduce your risk of developing the disease.
Colorectal cancer usually develops from pre-cancerous polyps called adenomatous polyps or serrated polyps. A polyp is a grape-like growth on the inside wall of the colon or rectum. Polyps grow slowly over many years. Most people do not develop polyps until after the age of 50 if they have an average risk for colorectal cancer (see below).
Some polyps become cancerous, others do not. In order to reduce the likelihood of colorectal cancer, it is important to get screened to find out if you have polyps and to have them removed if you do.
With regular colorectal cancer screening, more than one-third of colorectal cancer deaths could be avoided.
Along with regular screening, healthy lifestyle choices are the best current preventive measures against colorectal cancer. Here’s how you can help reduce your risk:
- Eat more foods that are high in fiber, including whole grains, fruits, vegetables.
- Eat more cruciferous vegetables, such as cabbage, broccoli, cauliflower, brussels sprouts.
- Increase calcium intake with low-fat milk, shellfish, salmon, calcium supplements with vitamin D.
- Decrease fats oils, butter, red meats.
- Limit your intake of charcoal broiled foods and avoid salt-cured foods.
- Exercise regularly.
- Do not smoke.
- Keep your body mass index in the normal range.
Symptoms of Colorectal Cancer
Colorectal cancer usually begins with no symptoms at all. However, over time, there are a number of warning signs that can occur such as:
- Rectal bleeding.
- Blood in your stool (bright red, black or very dark).
- A temporary change in your bowel movements, especially in the shape of the stool (e.g., narrow like a pencil).
- Discomfort in having a bowel movement or the urge to move your bowels without having a bowel movement.
- Frequent cramping pain in your lower abdomen.
- Frequent gas pains.
- Weight loss without dieting.
- Constant fatigue.
What Should I Do if I Have These Symptoms?
Call your gastroenterologist and schedule an appointment. He or she will ask questions about your symptoms and determine the best diagnostic test for you.
To help you understand and manage your condition, the AGA Institute provides you with the following information, designed to give you some basic facts, to help you better understand your condition and to serve as a starting point for discussions with your doctor.
Colorectal Cancer Risk Factors
You may be at average or increased risk for colorectal cancer, depending on your age and family medical history.
You are at average risk for colorectal cancer if you are age 50 or older and have none of the following risk factors.
Increased Risk Factors
You are at increased risk for colorectal cancer if you have:
- Personal history of colorectal cancer or polyps (adenomatous or serrated).
- Family history one or more parents, siblings, or children with colorectal cancer or polyps (adenomatous or serrated).
- Family history of multiple cancers, including colorectal cancer, and those involving the uterus, ovary and other organs.
- Personal history of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease.
- Inherited syndrome such as Familial Adenomatous Polyposis (FAP), which leads to hundreds of polyps in the colon or rectum during the teen years; generally one of these develops into cancer by age 30.
- Lynch Syndrome (Hereditary Non-Polyposis Colon Cancer), which is not characterized by a large number of polyps as a warning sign, but often includes a family history of colorectal cancer among multiple family members in multiple generations.
Gender Is Not a Risk Factor
There is a common misperception that women are less likely to get colorectal cancer than men, but men and women are equally affected by colorectal cancer.
In fact, colorectal cancer is the third-leading cause of cancer death in women, behind breast and lung cancer. More than 71,000 women are diagnosed with colorectal cancer each year and nearly 26,000 die from the disease.
Colorectal Cancer Screening Tests
Adapted from Levin B., Lieberman DA., McFarland B. et al. Screening and Surveillance for the Early Detection of Colorectal Cancer and
Adenomatous Polyps, 2008: A Joint Guideline From the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer,
and the American College of Radiology. Gastroenterology. 2008 May;134(5):1570-95.
This procedure involves the examination of the colon by use of a long, flexible, lighted tube called the colonoscope through which the doctor can view the entire colon and rectum for polyps or cancer and during the same exam remove pre-cancerous polyps. It is the test most gastroenterologists recommend as the single best screening exam for colorectal cancer. It is the only method that combines both screening and prevention (by removal of pre-cancerous polyps).
The colonoscope has a camera at the end, which can project images on a screen. If a polyp is found, it can be removed by a wire loop that is passed through the colonoscope and hooked around the base of the polyp. The doctor sends an electric current through the loop, which severs the polyp from the colon wall and pulls it out of the colon. The polyp is then sent to a laboratory to be tested to determine whether it is cancerous. This procedure requires patients to be sedated.
A colonoscopy can be performed safely in an ambulatory surgical center, an outpatient office or a hospital setting. Patients do not have to be hospitalized. Some pressure may be felt from the instrument’s movements during the exam and there may be some cramping afterwards. Occasionally traces of blood will be seen in the stool after the procedure if a biopsy was taken or a polyp was removed. If you have more than a tablespoon of blood, you should call your doctor.
- When to have this test: Recommended every 10 years after age 50 for average-risk individuals. Patients at higher risk for colorectal cancer, including those with a family history, or with polyps or other diseases, should talk to your gastroenterologist about appropriate screening intervals. Read the AGA Choosing Wisely® Report, “Colonoscopy: When you need it—and when you don’t,” for more information.
- Test preparation: Your doctor will prescribe a diet, often clear liquids, for the day prior to your examination. Laxatives and/or enemas will be required. For more information on colonoscopy, read the AGA Institute brochure on that topic at www.gastro.org/patient.
Fecal Immunohistochemical Test (FIT)
FIT is a test that can detect hidden blood in the stool with great accuracy. The test is available in a kit with which you can collect the stool samples at home and send them into a laboratory to test for blood coming from your colon. FIT is relatively easy to perform and inexpensive. It can only detect early cancers, not pre-cancerous polyps. You do not have to follow a special diet. If the FIT test is abnormal, you will require a regular colonoscopy for further evaluation.
- When to have this test: It is recommended annually for persons beginning at age 50. If the test is positive, your doctor may recommend a colonoscopy examination.
- Test preparation: FIT does not require a restricted diet.
Fecal Occult Blood Test (FOBT)
In this procedure, stool is tested in a laboratory for the presence of occult or hidden blood. The test is available in a kit with which you can collect the stool samples at home. You will need to follow a special diet when collecting your samples. This test, which is relatively easy and inexpensive, is designed to test for early cancers, but it does not detect pre-cancerous polyps. If the FOBT is abnormal, you will require a regular colonoscopy for further evaluation.
When to have this test: It is recommended annually for persons beginning at age 50. If the test is positive, your doctor may recommend a colonoscopy examination.
- Test preparation: Avoid these items in your diet for two days prior to the test as they may affect the test results:
- Red meat
- Vitamin C supplements
- Foods containing iron
- Aspirin, which can irritate the stomach
Sigmoidoscopy is a test during which a doctor uses a short, flexible, lighted tube to check the rectum and the lower end of the colon for polyps and cancer. If a polyp or abnormality is found, you may require a regular colonoscopy for further evaluation. This test can be performed in a doctor’s office and does not require anesthesia or sedation. You will need to take a cleansing enema prior to the procedure. Insertion of the flexible tube may be somewhat uncomfortable and some cramping may occur during the procedure. After the test, there may be some mild
abdominal gas pains. If the doctor took a biopsy, some traces of blood may be in the stool for a few days after the procedure.
- When to have this test: This test is recommended every five years beginning at age 50 unless colonoscopies are being done.
- Test preparation: One or two mild enemas are given prior to the test.
Computed Tomographic (CT) Colonography
This test involves an examination of your colon and rectum using a CT scanner to take pictures of your colon. A computer is used to combine the pictures creating both 2- and 3-dimensional views that allow a specially trained physician to “fly through” images of your colon and rectum to look for polyps and cancer. This procedure does not require sedation, but may be somewhat uncomfortable because air is put in your colon during the exam. You will need to take a preparation to cleanse your colon, much the same as for a regular colonoscopy, prior to the test.
At the beginning of the test, a small flexible tube will be inserted into your rectum to introduce air into your colon. A CT colonography can be performed in an outpatient imaging center, an outpatient office or a hospital setting. If a polyp or other abnormality is discovered during the CT colonography, you will require a regular colonoscopy to biopsy or remove the abnormality or polyp.
- When to have this test: Recommended every five years for average risk individuals. Patients at higher risk for colorectal cancer, including those with a family history, or with polyps or other diseases, should talk to your gastroenterologist about whether a regular colonoscopy may be a more appropriate screening method.
- Test preparation: Your doctor will prescribe a diet, often clear liquids, for the day prior to your examination. Laxatives and/or enemas will be required just like the preparation for a regular colonoscopy. You should check with your insurance company about coverage.
Stool DNA (sDNA)
In this procedure, stool is tested in a laboratory to look for genetic DNA mutations. Colorectal cancer cells that contain genetic DNA mutations are shed into the large bowel and passed into the stool. The test is not currently available in the U.S. It uses a special kit with which you collect the stool sample at home. You must have access to a working freezer as the stool specimen will need to be submitted back to the lab along with a specially designed ice pack. If the sDNA test is abnormal, you will require a colonoscopy for further evaluation.
- When to have this test: All people over age 50 should be tested for colorectal cancer. If the test is positive, your doctor may recommend a colonoscopy examination. The screening interval for sDNA is unknown at this time and most insurance does not cover this test.
- Test preparation: Since sDNA detects DNA in stool, preparation does not require a restricted diet.
Digital Rectal Examination
A FOBT or FIT done during a digital rectal exam in the doctor’s office is not adequate for screening.
Talk to your gastroenterologist to make an informed decision about which screening tests are right for you.