Colorectal Cancer Screening: What to Know
Colorectal cancer affects the colon or rectum and is one of the most commonly diagnosed cancers in the United States. Screening can find colorectal cancer early, when treatment is more likely to be successful. Some screening tests can also find precancerous polyps so they can be removed before they become cancer.
For adults at average risk, regular colorectal cancer screening should generally begin at age 45. Most adults should continue screening through age 75. From ages 76 to 85, the decision to continue screening depends on factors such as overall health, previous screening results, and personal preferences.
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What does screening involve?
There are several ways to screen for colorectal cancer. The right test depends on your preferences, medical history, risk factors, and access to testing.
One option is a fecal immunochemical test, or FIT. This is a stool test that can usually be completed at home. You collect a small stool sample using the kit provided and send or return it to a laboratory for testing.
FIT looks for small amounts of blood in the stool that cannot be seen with the naked eye. Blood may come from colorectal cancer or a polyp, but it can also be caused by other conditions.
For people who choose FIT, the test is generally repeated every year.
Other screening options include:
- Colonoscopy every 10 years
- Stool DNA-FIT testing at recommended intervals
- CT colonography every 5 years
- Flexible sigmoidoscopy at recommended intervals
A colonoscopy allows a doctor to examine the inside of the colon and rectum and remove certain polyps during the procedure.
What happens if a screening test is abnormal?
An abnormal FIT or other non-colonoscopy screening test does not necessarily mean you have cancer. Blood in the stool can have other causes.
However, an abnormal stool-based screening test should be followed by a colonoscopy. A colonoscopy allows the doctor to look directly at the colon and rectum and determine whether polyps, cancer, or another condition may be causing the abnormal result.
If polyps are found, they may be removed during the colonoscopy and sent to a laboratory for testing. Your doctor will recommend future screening or surveillance based on what is found.
What if I have symptoms?
Screening is intended for people who do not have symptoms.
If you develop possible symptoms of colorectal cancer, do not wait until your next screening test. Contact your doctor so the cause can be evaluated.
Possible symptoms include:
- Blood in or on the stool
- A persistent change in bowel habits, such as diarrhea or constipation
- Feeling that your bowel does not empty completely
- Ongoing abdominal pain or cramping
- Unexplained weight loss
- Iron-deficiency anemia
These symptoms can have many causes other than cancer, but they should be evaluated, especially if they are new or persistent.
A previous negative screening test does not rule out every possible cause of new symptoms.
What if I have a higher risk of colorectal cancer?
Some people may need to begin screening before age 45, be screened more often, or use a particular type of test.
You may be at increased risk if you have:
- A personal or family history of colorectal cancer or certain colorectal polyps
- Inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
- A hereditary condition such as Lynch syndrome or familial adenomatous polyposis (FAP)
- A history of certain colorectal polyps found during a previous colonoscopy
Talk with your doctor about when screening should begin and which test and schedule are appropriate for you.
Lifestyle factors can also affect colorectal cancer risk. Regular physical activity, maintaining a healthy weight, avoiding tobacco, and limiting alcohol can help lower risk.
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