Colorectal Cancer: Which Screening Test Should I Have?

You may want to have a say in this decision, or you may simply want to follow your doctor's recommendation. Either way, this information will help you understand what your choices are so that you can talk to your doctor about them.

Colorectal Cancer: Which Screening Test Should I Have?

Get the facts

Your options

  • Get a stool test every 1 or 2 years.
  • Get a stool test at the recommended time and a sigmoidoscopy every 5 years.
  • Get a colonoscopy every 10 years.

Key points to remember

  • No matter what test you use, regular testing lowers your risk of getting and dying from colorectal cancer. Screening can find cancer early, when it can be treated and often cured.
  • The tests differ in how they are done, how often they are done, and how you prepare for them. Your preferences are important in choosing what test to have. Think about what matters most to you as you look at what each test involves.
  • No matter which test you choose, it's important that you have the test on the recommended schedule and have any follow-up visits or tests as needed. That gives you the best chance of reducing the risk of dying from colorectal cancer.
  • Routine testing is recommended for everyone age 50 and older who has an average risk for colorectal cancer. Your doctor may recommend getting tested earlier or more often if you have a higher risk. If you are older than 75 or have serious health problems, you and your doctor might decide that it's best for you not to be screened.
FAQs

What is colorectal cancer?

Colorectal cancer happens when cells that are not normal grow in your colon or rectum. Most people just call it "colon cancer."

These cancers usually begin as polyps. Polyps are growths attached to the inside of the colon or rectum. Colon polyps are common. Most of them don't turn into cancer. Polyps are found during some screening tests. And polyps found during a colonoscopy usually can be removed at the same time.

Why is regular screening important?

Colorectal cancer is easier to treat when it is found early through screening tests.

With colorectal cancer, symptoms often don't show up until the cancer is advanced. So regular screening—no matter what test you choose—makes it more likely that cancer will be found early.

Why is your family history important?

A family history of colorectal cancer makes you more likely to get it. You may need to be screened at an earlier age—and be tested more often—than other people if:

  • You have a close relative with colorectal cancer. You are more likely to get colorectal cancer if:
    • One of your parents, brothers, sisters, or children had it before the age of 60.
    • Two or more of your parents, brothers, sisters, or children had it at any age.
  • You have a family history of certain colon problems. These include familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC). Most people who inherit these conditions will get colorectal cancer if they are not screened and treated.

What are stool tests?

Stool tests involve sending some of your stool to a lab for testing. The tests look for blood in the stool, which can be a sign of colorectal cancer.

Most stool tests need to be done once a year. These tests can usually be done in your home.

There are different types of stool tests:

  • Fecal occult blood test (FOBT). This is the most common stool test. You put tiny samples of your stool on a special card or cloth and send it to a lab. The lab uses certain chemicals to find blood that you can't see with the naked eye.
  • Fecal immunochemical test (FIT). This test is a little easier to do at home. It also looks for signs of blood in the stool.

You can get an at-home stool test from your doctor or your local drugstore. But you may feel better if you talk to your doctor about what the test results mean.

Risks of stool tests

There is no risk from the stool test itself. The test just involves putting a sample of stool on a card or collecting a stool sample.

But there are some things you need to think about. If your test is positive, you will need to have a colonoscopy. This would be used to see if the stool test result is from colorectal cancer. But blood in the stool is more often caused by something other than cancer. These reasons could include hemorrhoids, ulcers, or taking aspirin. A positive test result from these things could lead you to worry. And you would end up having a colonoscopy.

What is a stool DNA test?

A stool DNA (sDNA) test involves sending some of your stool to a lab. The test is used to look for blood in the stool and genetic changes in DNA that could be a sign of cancer.

This is the newest stool test. It is still being studied to see how well it works to find or prevent colorectal cancer.

If you are interested in learning more about a stool DNA test, talk to your doctor.

What is sigmoidoscopy?

Sigmoidoscopy (say "sig-moy-DAW-skuh-pee") is a test that lets your doctor look at the inside of the lower part of your colon. The doctor looks through a lighted tube that can bend around the corners of the colon.

When used to screen for colorectal cancer, this test is usually done every 5 years. Most people who get this test also get a yearly stool test.

Getting ready for a sigmoidoscopy involves cleaning out the colon.

  • For 1 to 2 days before the test, you may be on a clear liquid diet.
  • You will likely have an enema before the test.

This test usually takes 5 to 15 minutes. It may take slightly longer if polyps are found and removed.

Risks of sigmoidoscopy

There is a small risk of problems from having a sigmoidoscopy.

There is a slight chance of piercing the colon (perforation) or causing severe bleeding by damaging the wall of the colon. But this is rare. There is also a very rare chance of a colon infection.

A sigmoidoscopy only looks at the lower part of your colon, which is where most polyps grow. But sometimes polyps grow in the upper part of your colon. Those polyps would not be seen with this test.

If your doctor finds polyps during a sigmoidoscopy, you will need to have a colonoscopy to see if there are more polyps farther up in your colon. And that test also has possible risks.

What is colonoscopy?

Colonoscopy (say "koh-luh-NAW-skuh-pee") is a test that lets your doctor look at the inside of your entire colon. The doctor looks through a lighted tube that can bend around the corners of the colon.

With this test, the doctor can find and remove polyps, which are growths inside the colon that can turn into colorectal cancer.

When used as a screening test for colorectal cancer, this test is usually done every 10 years. If you have a colonoscopy, you won't need to have a yearly stool test. A colonoscopy may be done more often if your risk is higher than average.

Getting ready for a colonoscopy involves a very thorough cleansing of the colon. The colon must be completely empty.

  • For 1 to 2 days before the test, you will be on a clear liquid diet.
  • On the night before the test, your doctor may have you take a prescription laxative tablet or drink a large container of laxative solution. This will make you use the bathroom often.

During the test, you may be given medicine to help you relax. Many people don't remember the test afterward because they are so relaxed.

The test usually takes 30 to 45 minutes. But it may take longer if polyps are found and removed.

Risks of colonoscopy

There is a small risk of problems from having a colonoscopy. The scope or a small tool may tear the lining of the colon or cause bleeding. Although these problems are rare, they happen more often with colonoscopy than with sigmoidoscopy.footnote 1

What is a virtual colonoscopy?

A virtual colonoscopy uses pictures taken during a CT scan to look at the colon. A thin tube is inserted into the rectum, and air is pumped through the tube into the colon. The air expands the colon so that it is easier to see on an X-ray.

This test is not done everywhere, so it may not be an option for many people.

Getting ready for a virtual colonoscopy involves the same cleansing of the colon that is needed for a regular colonoscopy.

Virtual colonoscopy is still being studied to see how well it works to find or prevent colorectal cancer. If anything is found, you will need a regular colonoscopy to make sure that you don't have cancer. Any polyps found also will be removed.

If you want to learn more about virtual colonoscopy, talk to your doctor.

What do numbers tell us about the benefits and risks of colorectal cancer screening tests?

Benefits of screening tests

Colorectal cancers and deaths avoided because of screening for people ages 50 to 74*footnote 1
Screening test People who avoid colorectal cancer over 30 years because of screening People who avoid colorectal cancer deaths over 30 years because of screening
Stool test (FIT) every year or two 41 out of 1,000 people 13 out of 1,000 people
Sigmoidoscopy every 5 years and FIT as recommended 44 out of 1,000 people 14 out of 1,000 people
Colonoscopy every 10 years 46 out of 1,000 people 14 out of 1,000 people

*Based on the best available evidence (evidence quality: high)

Colorectal cancer screening can help reduce your risk of getting colorectal cancer.footnote 1Take a group of 1,000 people ages 50 to 74.

  • With a stool test every year, 41 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a sigmoidoscopy every 5 years and a stool test every year, 44 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a colonoscopy every 10 years, 46 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.

Colorectal cancer screening can help reduce cancer deaths.footnote 1Take a group of 1,000 people ages 50 to 74.

  • With a stool test every year, 13 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a sigmoidoscopy every 5 years and a stool test every year, 14 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a colonoscopy every 10 years, 14 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.

Risks of screening tests

Risks of colorectal cancer screening testsfootnote 2, footnote 3
Screening test Risk of major complications (a hole or tear in the colon or serious bleeding)
Stool tests About 0.3 out of 1,000 people (or 3 out of 10,000 people) had a tear or bleeding—not from the stool test itself, but from follow-up colonoscopy.
Sigmoidoscopy About 0.8 out of 1,000 people (or 8 out of 10,000 people) had a tear or bleeding. This includes problems from follow-up colonoscopy.
Colonoscopy About 2.6 out of 1,000 people (or 26 out of 10,000 people) had a tear or bleeding from the procedure.

Screening tests have some risk of creating a hole or tear (perforation) in the colon . There is also a chance of bleeding. Both of these risks are small. footnote 2, footnote 3The quality of this evidence is high.

  • A major complication (serious bleeding or a hole or tear in the colon) happens after a stool test in about 3 out of every 10,000 people. This is not from the stool test itself. It's from the follow-up colonoscopy or surgery after a "positive" stool test. This means that about 9,997 out of every 10,000 people don't have a serious problem.
  • A tear or serious bleeding from sigmoidoscopy happens in about 8 out of every 10,000 people. So about 9,992 out of every 10,000 people don't have any serious problems.
  • Serious problems from a colonoscopy happen in about 26 out of every 10,000 people. This means that about 9,974 out of every 10,000 people don't have a serious problem.

The risk of dying from a problem caused by a screening test is very rare.

Understanding the evidence

Some evidence is better than other evidence. Evidence comes from studies that look at how well treatments and tests work and how safe they are. For many reasons, some studies are more reliable than others. The better the evidence is—the higher its quality—the more we can trust it.

The information shown here is based on the best available evidence.footnote 1footnote 2footnote 4footnote 3 The evidence is rated using four quality levels: high, moderate, borderline, and inconclusive.

Another thing to understand is that the evidence can't predict what's going to happen in your case. When evidence tells us that 2 out of 100 people who have a certain test or treatment may have a certain result and that 98 out of 100 may not, there's no way to know if you will be one of the 2 or one of the 98.

What do experts recommend?

Experts recommend stool tests, sigmoidoscopy or sigmoidoscopy with stool tests, or colonoscopy to screen for colorectal cancer.

Recommendations from the U.S. Preventive Services Task Force

  • People ages 50 to 75 should have a fecal occult blood test (FOBT), sigmoidoscopy, or colonoscopy.
  • People who have a sigmoidoscopy every 5 years also should have a stool test (FOBT) every year (or every 3 years for the stool DNA test).
  • Some people older than 75 may benefit from screening tests. Others may not. Talk to your doctor about continuing testing for colorectal cancer after age 75.

Recommendations from other groups

  • The American Cancer Society (ACS), the American Gastroenterological Association (AGA), and the American College of Gastroenterologists (ACG) recommend routine testing for people age 50 and older who have a normal risk for colorectal cancer.
  • Your doctor may recommend being tested earlier or more often if you have a higher risk for colorectal cancer. Talk to your doctor about when you should be tested.

Compare your options

Compare

What is usually involved?









What are the benefits?









What are the risks and side effects?









Stool test Stool test
  • You do this every year or two, depending on the test.
  • It's done at home.
  • You take samples of your stool and mail them to a lab.
  • It's easy to do at home.
  • It's cheaper than other tests.
  • You don't need to use laxatives or enemas.
  • A "positive" result means you will need a colonoscopy, which also has risks.
  • You may have a "positive" result from conditions that are not cancer, such as hemorrhoids and colon polyps. This could lead to worry and having a colonoscopy to make sure that you don't have cancer.
Sigmoidoscopy Sigmoidoscopy
  • You have this test every 5 years, often along with a yearly stool test.
  • It's done in a doctor's office, clinic, or hospital.
  • It takes 5 to 15 minutes. It may take slightly longer if polyps are removed.
  • You don't have to do it as often as a stool test.
  • It can find polyps before they turn into cancer.
  • It has fewer risks than colonoscopy.
  • This test only sees the lower part of the colon.
  • Rare problems include bleeding problems and piercing the colon (perforation).
  • There may be some discomfort during the test.
  • If polyps are found, you will need a colonoscopy to check the rest of your colon.
Colonoscopy Colonoscopy
  • You have this every 10 years. It will likely be done more often if you have risk factors for colorectal cancer or if polyps are found.
  • It's done in a doctor's office, clinic, or hospital.
  • You use laxatives to clean out your bowels.
  • It takes 30 to 45 minutes, or slightly longer if polyps are removed.
  • You are given drugs to relax. You may not remember the test at all.
  • You don't have to do it as often as other tests.
  • It can find polyps before they turn into cancer.
  • Polyps usually can be removed during the test.
  • This test looks at your entire colon.
  • It costs more than other tests.
  • Bleeding problems and piercing the colon are rare but are more common than with sigmoidoscopy.

Personal stories about test methods for colorectal cancer

These stories are based on information gathered from health professionals and consumers. They may be helpful as you make important health decisions.

My friend died of colon cancer, so I think I am going to have a colonoscopy. I know that colonoscopy may have slightly greater risks of complications than a sigmoidoscopy. But I would rather have a colonoscopy to make sure I don't have cancer.

Edna, age 55

I've had a fecal occult blood test every year, and now I'm also going to have a sigmoidoscopy. I am a little worried and embarrassed about having a sigmoidoscopy. But I would rather be a little embarrassed than have colon cancer.

Jose Luis, age 54

I didn't care for the prep for the colonoscopy. You have to drink lots of fluid, and it takes a long time. But the test itself was no big deal. They didn't find any polyps. So now that I've had the test, I like knowing that I don't have to do this again for 10 years.

Frank, age 52

A sigmoidoscopy is a good way for my doctor to look for signs of cancer. And there are fewer risks than with colonoscopy. I know it can't be used to look at the whole colon, but I'm also having a stool test.

Stella, age 58

No one in my family has ever had colon cancer. I try to eat a balanced diet and get plenty of exercise. I am going to do yearly stool tests. I am more comfortable doing that than having more costly procedures. And there are fewer risks.

Patrick, age 56

What matters most to you?

Your personal feelings are just as important as the medical facts. Think about what matters most to you in this decision, and show how you feel about the following statements.

I'm afraid of a test that involves putting anything into my colon.

Not important
Somewhat important
Very important

I want to have a test that is going to see as much as possible.

Not important
Somewhat important
Very important

It's important to me to do testing at home, in private.

Not important
Somewhat important
Very important

I don't like the idea of drinking a lot of laxative solution and spending a long time in the bathroom before a test.

Not important
Somewhat important
Very important

I don't want to miss any work for this test.

Not important
Somewhat important
Very important

I want to get the test over with and not think about it for another 10 years.

Not important
Somewhat important
Very important

I'm worried about the cost of the test.

Not important
Somewhat important
Very important

My other important reasons:

Not important
Somewhat important
Very important

Where are you leaning now?

Now that you've thought about the facts and your feelings, you may have a general idea of where you stand on this decision. Show which way you are leaning right now.

Using stool test

NOT using stool test

Leaning toward
Undecided
Leaning toward

Using sigmoidoscopy

NOT using sigmoidoscopy

Leaning toward
Undecided
Leaning toward

Using colonoscopy

NOT using colonoscopy

Leaning toward
Undecided
Leaning toward

What else do you need to make your decision?

Check the facts

1.

Will having regular screening tests lower your chances of dying from colorectal cancer?

  • Yes That's right. When colorectal cancer is found early through screening tests, it is more easily treated.
  • No Sorry, that's not right. When colorectal cancer is found early through screening tests, it is more easily treated.
  • I'm not sure It may help to go back and read "Get the Facts." When colorectal cancer is found early through screening tests, it is more easily treated.
2.

Is colonoscopy a lot better at preventing deaths from cancer than the other screening tests?

  • Yes Sorry, that's not right. All of the screening tests are good at preventing deaths from colorectal cancer. They differ in how they are done, how often they are done, and how you prepare for them.
  • No That's right. All of the screening tests are good at preventing deaths from colorectal cancer. They differ in how they are done, how often they are done, and how you prepare for them.
  • I'm not sure It may help to go back and read "Get the Facts." All of the screening tests are good at preventing deaths from colorectal cancer. They differ in how they are done, how often they are done, and how you prepare for them.
3.

Does having a stool test mean that I won't need to have a colonoscopy?

  • Yes That's not right. If blood is found in your stool, you need to have a colonoscopy to make sure that the blood isn't caused by cancer.
  • No That's right. If blood is found in your stool, you need to have a colonoscopy to make sure that the blood isn't caused by cancer.
  • I'm not sure It may help to go back and read "Get the Facts." If blood is found in your stool, you need to have a colonoscopy to make sure that the blood isn't caused by cancer.

Decide what's next

1.

Do you understand the options available to you?

2.

Are you clear about which benefits and side effects matter most to you?

3.

Do you have enough support and advice from others to make a choice?

Certainty

1.

How sure do you feel right now about your decision?

Not sure at all
Somewhat sure
Very sure

Your Summary

Here's a record of your answers. You can use it to talk with your doctor or loved ones about your decision.

Your decision  

Next steps

Which way you're leaning

How sure you are

Your comments

Your knowledge of the facts  

Key concepts that you understood

Key concepts that may need review

Getting ready to act  

Patient choices

Credits

Credits
Author Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Kenneth Bark, MD - General Surgery, Colon and Rectal Surgery
You may want to have a say in this decision, or you may simply want to follow your doctor's recommendation. Either way, this information will help you understand what your choices are so that you can talk to your doctor about them.

Colorectal Cancer: Which Screening Test Should I Have?

Here's a record of your answers. You can use it to talk with your doctor or loved ones about your decision.
  1. Get the facts
  2. Compare your options
  3. What matters most to you?
  4. Where are you leaning now?
  5. What else do you need to make your decision?

1. Get the Facts

Your options

  • Get a stool test every 1 or 2 years.
  • Get a stool test at the recommended time and a sigmoidoscopy every 5 years.
  • Get a colonoscopy every 10 years.

Key points to remember

  • No matter what test you use, regular testing lowers your risk of getting and dying from colorectal cancer. Screening can find cancer early, when it can be treated and often cured.
  • The tests differ in how they are done, how often they are done, and how you prepare for them. Your preferences are important in choosing what test to have. Think about what matters most to you as you look at what each test involves.
  • No matter which test you choose, it's important that you have the test on the recommended schedule and have any follow-up visits or tests as needed. That gives you the best chance of reducing the risk of dying from colorectal cancer.
  • Routine testing is recommended for everyone age 50 and older who has an average risk for colorectal cancer. Your doctor may recommend getting tested earlier or more often if you have a higher risk. If you are older than 75 or have serious health problems, you and your doctor might decide that it's best for you not to be screened.
FAQs

What is colorectal cancer?

Colorectal cancer happens when cells that are not normal grow in your colon or rectum . Most people just call it "colon cancer."

These cancers usually begin as polyps. Polyps are growths attached to the inside of the colon or rectum. Colon polyps are common. Most of them don't turn into cancer. Polyps are found during some screening tests. And polyps found during a colonoscopy usually can be removed at the same time.

Why is regular screening important?

Colorectal cancer is easier to treat when it is found early through screening tests.

With colorectal cancer, symptoms often don't show up until the cancer is advanced. So regular screening—no matter what test you choose—makes it more likely that cancer will be found early.

Why is your family history important?

A family history of colorectal cancer makes you more likely to get it. You may need to be screened at an earlier age—and be tested more often—than other people if:

  • You have a close relative with colorectal cancer. You are more likely to get colorectal cancer if:
    • One of your parents, brothers, sisters, or children had it before the age of 60.
    • Two or more of your parents, brothers, sisters, or children had it at any age.
  • You have a family history of certain colon problems. These include familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC). Most people who inherit these conditions will get colorectal cancer if they are not screened and treated.

What are stool tests?

Stool tests involve sending some of your stool to a lab for testing. The tests look for blood in the stool, which can be a sign of colorectal cancer.

Most stool tests need to be done once a year. These tests can usually be done in your home.

There are different types of stool tests:

  • Fecal occult blood test (FOBT). This is the most common stool test. You put tiny samples of your stool on a special card or cloth and send it to a lab. The lab uses certain chemicals to find blood that you can't see with the naked eye.
  • Fecal immunochemical test (FIT). This test is a little easier to do at home. It also looks for signs of blood in the stool.

You can get an at-home stool test from your doctor or your local drugstore. But you may feel better if you talk to your doctor about what the test results mean.

Risks of stool tests

There is no risk from the stool test itself. The test just involves putting a sample of stool on a card or collecting a stool sample.

But there are some things you need to think about. If your test is positive, you will need to have a colonoscopy. This would be used to see if the stool test result is from colorectal cancer. But blood in the stool is more often caused by something other than cancer. These reasons could include hemorrhoids, ulcers, or taking aspirin. A positive test result from these things could lead you to worry. And you would end up having a colonoscopy.

What is a stool DNA test?

A stool DNA (sDNA) test involves sending some of your stool to a lab. The test is used to look for blood in the stool and genetic changes in DNA that could be a sign of cancer.

This is the newest stool test. It is still being studied to see how well it works to find or prevent colorectal cancer.

If you are interested in learning more about a stool DNA test, talk to your doctor.

What is sigmoidoscopy?

Sigmoidoscopy (say "sig-moy-DAW-skuh-pee") is a test that lets your doctor look at the inside of the lower part of your colon. The doctor looks through a lighted tube that can bend around the corners of the colon.

When used to screen for colorectal cancer, this test is usually done every 5 years. Most people who get this test also get a yearly stool test.

Getting ready for a sigmoidoscopy involves cleaning out the colon.

  • For 1 to 2 days before the test, you may be on a clear liquid diet.
  • You will likely have an enema before the test.

This test usually takes 5 to 15 minutes. It may take slightly longer if polyps are found and removed.

Risks of sigmoidoscopy

There is a small risk of problems from having a sigmoidoscopy.

There is a slight chance of piercing the colon (perforation) or causing severe bleeding by damaging the wall of the colon. But this is rare. There is also a very rare chance of a colon infection.

A sigmoidoscopy only looks at the lower part of your colon, which is where most polyps grow. But sometimes polyps grow in the upper part of your colon. Those polyps would not be seen with this test.

If your doctor finds polyps during a sigmoidoscopy, you will need to have a colonoscopy to see if there are more polyps farther up in your colon. And that test also has possible risks.

What is colonoscopy?

Colonoscopy (say "koh-luh-NAW-skuh-pee") is a test that lets your doctor look at the inside of your entire colon . The doctor looks through a lighted tube that can bend around the corners of the colon.

With this test, the doctor can find and remove polyps, which are growths inside the colon that can turn into colorectal cancer.

When used as a screening test for colorectal cancer, this test is usually done every 10 years. If you have a colonoscopy, you won't need to have a yearly stool test. A colonoscopy may be done more often if your risk is higher than average.

Getting ready for a colonoscopy involves a very thorough cleansing of the colon. The colon must be completely empty.

  • For 1 to 2 days before the test, you will be on a clear liquid diet.
  • On the night before the test, your doctor may have you take a prescription laxative tablet or drink a large container of laxative solution. This will make you use the bathroom often.

During the test, you may be given medicine to help you relax. Many people don't remember the test afterward because they are so relaxed.

The test usually takes 30 to 45 minutes. But it may take longer if polyps are found and removed.

Risks of colonoscopy

There is a small risk of problems from having a colonoscopy. The scope or a small tool may tear the lining of the colon or cause bleeding. Although these problems are rare, they happen more often with colonoscopy than with sigmoidoscopy.1

What is a virtual colonoscopy?

A virtual colonoscopy uses pictures taken during a CT scan to look at the colon. A thin tube is inserted into the rectum, and air is pumped through the tube into the colon. The air expands the colon so that it is easier to see on an X-ray.

This test is not done everywhere, so it may not be an option for many people.

Getting ready for a virtual colonoscopy involves the same cleansing of the colon that is needed for a regular colonoscopy.

Virtual colonoscopy is still being studied to see how well it works to find or prevent colorectal cancer. If anything is found, you will need a regular colonoscopy to make sure that you don't have cancer. Any polyps found also will be removed.

If you want to learn more about virtual colonoscopy, talk to your doctor.

What do numbers tell us about the benefits and risks of colorectal cancer screening tests?

Benefits of screening tests

Colorectal cancers and deaths avoided because of screening for people ages 50 to 74*1
Screening test People who avoid colorectal cancer over 30 years because of screening People who avoid colorectal cancer deaths over 30 years because of screening
Stool test (FIT) every year or two 41 out of 1,000 people 13 out of 1,000 people
Sigmoidoscopy every 5 years and FIT as recommended 44 out of 1,000 people 14 out of 1,000 people
Colonoscopy every 10 years 46 out of 1,000 people 14 out of 1,000 people

*Based on the best available evidence (evidence quality: high)

Colorectal cancer screening can help reduce your risk of getting colorectal cancer.1Take a group of 1,000 people ages 50 to 74.

  • With a stool test every year, 41 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a sigmoidoscopy every 5 years and a stool test every year, 44 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a colonoscopy every 10 years, 46 out of 1,000 people will avoid colorectal cancer over 30 years, compared with people who do not have any screening.

Colorectal cancer screening can help reduce cancer deaths.1Take a group of 1,000 people ages 50 to 74.

  • With a stool test every year, 13 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a sigmoidoscopy every 5 years and a stool test every year, 14 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.
  • With a colonoscopy every 10 years, 14 out of 1,000 people will avoid death from colorectal cancer over 30 years, compared with people who do not have any screening.

Risks of screening tests

Risks of colorectal cancer screening tests2, 3
Screening test Risk of major complications (a hole or tear in the colon or serious bleeding)
Stool tests About 0.3 out of 1,000 people (or 3 out of 10,000 people) had a tear or bleeding—not from the stool test itself, but from follow-up colonoscopy.
Sigmoidoscopy About 0.8 out of 1,000 people (or 8 out of 10,000 people) had a tear or bleeding. This includes problems from follow-up colonoscopy.
Colonoscopy About 2.6 out of 1,000 people (or 26 out of 10,000 people) had a tear or bleeding from the procedure.

Screening tests have some risk of creating a hole or tear (perforation) in the colon . There is also a chance of bleeding. Both of these risks are small. 2, 3The quality of this evidence is high.

  • A major complication (serious bleeding or a hole or tear in the colon) happens after a stool test in about 3 out of every 10,000 people. This is not from the stool test itself. It's from the follow-up colonoscopy or surgery after a "positive" stool test. This means that about 9,997 out of every 10,000 people don't have a serious problem.
  • A tear or serious bleeding from sigmoidoscopy happens in about 8 out of every 10,000 people. So about 9,992 out of every 10,000 people don't have any serious problems.
  • Serious problems from a colonoscopy happen in about 26 out of every 10,000 people. This means that about 9,974 out of every 10,000 people don't have a serious problem.

The risk of dying from a problem caused by a screening test is very rare.

Understanding the evidence

Some evidence is better than other evidence. Evidence comes from studies that look at how well treatments and tests work and how safe they are. For many reasons, some studies are more reliable than others. The better the evidence is—the higher its quality—the more we can trust it.

The information shown here is based on the best available evidence.1243 The evidence is rated using four quality levels: high, moderate, borderline, and inconclusive.

Another thing to understand is that the evidence can't predict what's going to happen in your case. When evidence tells us that 2 out of 100 people who have a certain test or treatment may have a certain result and that 98 out of 100 may not, there's no way to know if you will be one of the 2 or one of the 98.

What do experts recommend?

Experts recommend stool tests, sigmoidoscopy or sigmoidoscopy with stool tests, or colonoscopy to screen for colorectal cancer.

Recommendations from the U.S. Preventive Services Task Force

  • People ages 50 to 75 should have a fecal occult blood test (FOBT), sigmoidoscopy, or colonoscopy.
  • People who have a sigmoidoscopy every 5 years also should have a stool test (FOBT) every year (or every 3 years for the stool DNA test).
  • Some people older than 75 may benefit from screening tests. Others may not. Talk to your doctor about continuing testing for colorectal cancer after age 75.

Recommendations from other groups

  • The American Cancer Society (ACS), the American Gastroenterological Association (AGA), and the American College of Gastroenterologists (ACG) recommend routine testing for people age 50 and older who have a normal risk for colorectal cancer.
  • Your doctor may recommend being tested earlier or more often if you have a higher risk for colorectal cancer. Talk to your doctor about when you should be tested.

2. Compare your options

  Stool test Sigmoidoscopy
What is usually involved?
  • You do this every year or two, depending on the test.
  • It's done at home.
  • You take samples of your stool and mail them to a lab.
  • You have this test every 5 years, often along with a yearly stool test.
  • It's done in a doctor's office, clinic, or hospital.
  • It takes 5 to 15 minutes. It may take slightly longer if polyps are removed.
What are the benefits?
  • It's easy to do at home.
  • It's cheaper than other tests.
  • You don't need to use laxatives or enemas.
  • You don't have to do it as often as a stool test.
  • It can find polyps before they turn into cancer.
  • It has fewer risks than colonoscopy.
What are the risks and side effects?
  • A "positive" result means you will need a colonoscopy, which also has risks.
  • You may have a "positive" result from conditions that are not cancer, such as hemorrhoids and colon polyps. This could lead to worry and having a colonoscopy to make sure that you don't have cancer.
  • This test only sees the lower part of the colon.
  • Rare problems include bleeding problems and piercing the colon (perforation).
  • There may be some discomfort during the test.
  • If polyps are found, you will need a colonoscopy to check the rest of your colon.
  Colonoscopy
What is usually involved?
  • You have this every 10 years. It will likely be done more often if you have risk factors for colorectal cancer or if polyps are found.
  • It's done in a doctor's office, clinic, or hospital.
  • You use laxatives to clean out your bowels.
  • It takes 30 to 45 minutes, or slightly longer if polyps are removed.
  • You are given drugs to relax. You may not remember the test at all.
What are the benefits?
  • You don't have to do it as often as other tests.
  • It can find polyps before they turn into cancer.
  • Polyps usually can be removed during the test.
  • This test looks at your entire colon.
What are the risks and side effects?
  • It costs more than other tests.
  • Bleeding problems and piercing the colon are rare but are more common than with sigmoidoscopy.

Personal stories

Personal stories about test methods for colorectal cancer

These stories are based on information gathered from health professionals and consumers. They may be helpful as you make important health decisions.

"My friend died of colon cancer, so I think I am going to have a colonoscopy. I know that colonoscopy may have slightly greater risks of complications than a sigmoidoscopy. But I would rather have a colonoscopy to make sure I don't have cancer."

— Edna, age 55

"I've had a fecal occult blood test every year, and now I'm also going to have a sigmoidoscopy. I am a little worried and embarrassed about having a sigmoidoscopy. But I would rather be a little embarrassed than have colon cancer."

— Jose Luis, age 54

"I didn't care for the prep for the colonoscopy. You have to drink lots of fluid, and it takes a long time. But the test itself was no big deal. They didn't find any polyps. So now that I've had the test, I like knowing that I don't have to do this again for 10 years."

— Frank, age 52

"A sigmoidoscopy is a good way for my doctor to look for signs of cancer. And there are fewer risks than with colonoscopy. I know it can't be used to look at the whole colon, but I'm also having a stool test."

— Stella, age 58

"No one in my family has ever had colon cancer. I try to eat a balanced diet and get plenty of exercise. I am going to do yearly stool tests. I am more comfortable doing that than having more costly procedures. And there are fewer risks."

— Patrick, age 56

3. What matters most to you?

Your personal feelings are just as important as the medical facts. Think about what matters most to you in this decision, and show how you feel about the following statements.

I'm afraid of a test that involves putting anything into my colon.

         
Not important
Somewhat important
Very important

I want to have a test that is going to see as much as possible.

         
Not important
Somewhat important
Very important

It's important to me to do testing at home, in private.

         
Not important
Somewhat important
Very important

I don't like the idea of drinking a lot of laxative solution and spending a long time in the bathroom before a test.

         
Not important
Somewhat important
Very important

I don't want to miss any work for this test.

         
Not important
Somewhat important
Very important

I want to get the test over with and not think about it for another 10 years.

         
Not important
Somewhat important
Very important

I'm worried about the cost of the test.

         
Not important
Somewhat important
Very important

My other important reasons:

 
         
Not important
Somewhat important
Very important

4. Where are you leaning now?

Now that you've thought about the facts and your feelings, you may have a general idea of where you stand on this decision. Show which way you are leaning right now.

Using stool test

NOT using stool test

             
Leaning toward
Undecided
Leaning toward

Using sigmoidoscopy

NOT using sigmoidoscopy

             
Leaning toward
Undecided
Leaning toward

Using colonoscopy

NOT using colonoscopy

             
Leaning toward
Undecided
Leaning toward

5. What else do you need to make your decision?

Check the facts

1. Will having regular screening tests lower your chances of dying from colorectal cancer?

  • Yes
  • No
  • I'm not sure
That's right. When colorectal cancer is found early through screening tests, it is more easily treated.

2. Is colonoscopy a lot better at preventing deaths from cancer than the other screening tests?

  • Yes
  • No
  • I'm not sure
That's right. All of the screening tests are good at preventing deaths from colorectal cancer. They differ in how they are done, how often they are done, and how you prepare for them.

3. Does having a stool test mean that I won't need to have a colonoscopy?

  • Yes
  • No
  • I'm not sure
That's right. If blood is found in your stool, you need to have a colonoscopy to make sure that the blood isn't caused by cancer.

Decide what's next

1. Do you understand the options available to you?

2. Are you clear about which benefits and side effects matter most to you?

3. Do you have enough support and advice from others to make a choice?

Certainty

1. How sure do you feel right now about your decision?

         
Not sure at all
Somewhat sure
Very sure

2. Check what you need to do before you make this decision.

  • I'm ready to take action.
  • I want to discuss the options with others.
  • I want to learn more about my options.
 
Credits
By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Kenneth Bark, MD - General Surgery, Colon and Rectal Surgery

References
Citations
  1. Dinh T, et al. (2013). Health benefits and cost-effectiveness of a hybrid screening strategy for colorectal cancer. Clinical Gastroenterology and Hepatology, 11(9): 1158–1166. DOI: 10.1016/j.cgh.2013.03.013. Accessed January 13, 2015.
  2. Warren JL, et al. (2009). Adverse events after outpatient colonoscopy in the Medicare population. Annals of Internal Medicine, 150(12): 849–857. DOI: 10.7326/0003-4819-150-12-200906160-00008. Accessed February 2, 2015.
  3. Rabeneck L, et al. (2008). Bleeding and perforation after outpatient colonoscopy and their risk factors in usual clinical practice. Gastroenterology, 135(6): 1899–1906. DOI 10.1053/j.gastro.2008.08.058. Accessed February 13, 2015.
  4. Levin TR, et al. (2006). Complications of colonoscopy in an integrated health care delivery system. Annals of Internal Medicine, 145(12): 880–886. DOI: 10.7326/0003-4819-145-12-200612190-00004. Accessed February 2, 2015.

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