Colorectal cancer is cancer that begins in the colon (also called the "large intestine") or rectum. Colorectal cancer is more common among adults age 45 and older, but it can occur at an earlier age.
With regular screening, almost all colorectal cancer can be prevented.
Learn your health history and talk to your healthcare provider about getting screened for colorectal cancer.
Answers to common questions
- How does colorectal cancer develop?
- What can affect my chances of getting colorectal cancer?
- When should I get screened?
- Does colorectal cancer have any symptoms?
- Should I wait until I have symptoms to get screened?
- Do I have screening options?
- Is it common to find polyps during colorectal cancer screening?
- Is it common to find cancer during colorectal cancer screening?
- What can I do to lower my chances of getting colorectal cancer?
How does colorectal cancer develop?
Colorectal cancer almost always starts as a small polyp. A polyp is a small growth on the lining of the colon or rectum. Over 10-15 years, polyps can turn into cancer. With regular screening, polyps can be found and removed early – before they turn into cancer. If cancer is present, screening can find cancer early, when it is more treatable.
What can affect my chances of getting colorectal cancer?
- Screening: Getting regular colorectal cancer screening increases the chances that polyps can be found and removed before they become cancerous.
- Age: Colorectal cancer is most common in people 45 and older.
- Personal Health History: If you have had polyps, colorectal cancer, or inflammatory bowel disease (IBD), you may be more likely to get colorectal cancer in the future.
- Family Health History: If your parents, siblings, or children have had polyps or colorectal cancer, you may be more likely to have polyps or colorectal cancer.
- Genetics: Lynch Syndrome (Hereditary Non-Polyposis Colorectal Cancer) is one of a few uncommon genetic conditions that can increase the chances of developing colorectal cancer. These conditions are passed from parents to children through their genes. If you have several close relatives who have had a lot of polyps or colorectal cancer, your healthcare provider may suggest that you start colorectal cancer screening at an earlier age and that you get genetic testing.
- Health Behaviors: These behaviors can increase your chances of getting colorectal cancer:
- Using tobacco
- Drinking a lot of alcohol
- Eating a high-fat diet
- Eating a low-fiber diet
- Not exercising enough
When should I get screened?
The age to begin screening depends on your personal and family health history. Follow your healthcare provider’s advice about when to get screened for the first time and how often to repeat screening.
People at average risk for developing colorectal cancer generally start screening at age 45. You may be at average risk if you do not have a personal or family history of colorectal cancer or potentially pre-cancerous polyps.
If you do have a personal or family history of colorectal cancer or pre-cancerous polyps, you may be at increased risk of getting colorectal cancer. If you are at increased risk, your healthcare provider may recommend that you start getting screened at a younger age. Colonoscopy is the only appropriate screening for people at increased risk.
Does colorectal cancer have any symptoms?
Most people with polyps or colorectal cancer do not experience symptoms. This makes regular screening very important for finding polyps to remove them before they become cancer or to find cancer early. When cancer is found early, it is easier to treat and survival is improved.
Some people with colorectal cancer may have symptoms. Symptoms can be:
- Stomach pains that do not go away
- Bloody stool (blood in the toilet when having a bowel movement)
- Feeling like you still need to have a bowel movement, even after going to the bathroom
- Change in your bowel habits that does not go back to normal
- Losing a lot of weight when there is no other reason for the weight loss
Talk with your healthcare provider if you have these or any other potential symptoms.
Should I wait until I have symptoms to get screened?
No. You should not skip or delay screening because you don’t have symptoms. Skipping or delaying screening can result in polyps or cancer being found later, when they’re harder to treat.
Do I have screening options?
If you are at average risk for getting colorectal cancer, there are five ways you can get screened. Those screenings are:
- Colonoscopy - a doctor uses a thin, flexible tube to look for polyps and cancer throughout your colon and rectum
- Sigmoidoscopy - a doctor uses a thin, flexible tube to look for polyps and cancer in the lower part of your colon and rectum
- Computed Tomographic Colonography ("Virtual Colonoscopy") - a CT scan that creates images of your colon and rectum that a trained doctor can read
- Stool DNA Test (Colorguard®) - You collect a stool (poop) sample at home and send it to a lab. The lab will look for blood and DNA from colorectal cancer or precancerous polyps
- Stool Test (FIT/iFOBT/gFOBT) - You collect a stool (poop) sample at home and send it to a lab. The lab will look for blood in the stool
If you are at increased risk, you should be screening using colonoscopy.
Read more information about the five types of colorectal cancer screening (PDF)
Is it common to find polyps during colorectal cancer screening?
Yes, finding polyps is quite common. In fact, polyps are found in at least 250 people out of every 1,000 people who get a colonoscopy. Finding and painlessly removing these polyps during a colonoscopy can prevent them from growing into cancer.
Is it common to find cancer during colorectal cancer screening?
No. Finding cancer is not common. Cancer is found in only a few people out of every 1,000 average-risk people who get a colonoscopy for screening. In the unlikely case that colorectal cancer is present, with regular screening it is more likely that cancer will be found before it can spread. When cancer is caught and treated before it can spread, survival will be much improved.
What can I do to lower my chances of getting colorectal cancer?
- Talk with your healthcare provider to decide which screening is best for you. Then get screened.
- Learn your family health history so that you and your healthcare provider can make the best screening choice for your situation.
- Start or continue these healthy behaviors:
- Avoid tobacco
- Limit how much alcohol you drink
- Limit high-fat, low-fiber foods like red meat and hotdogs
- Eat plenty of low-fat, high-fiber foods like fruits and vegetables
- Exercise regularly
- Maintain a healthy body weight
Remember: With regular screening, almost all colorectal cancer can be prevented. Talk with your healthcare provider to get screened.
Special thanks to the New Hampshire Colorectal Cancer Screening Program and the many Norris Cotton Cancer Center volunteers whose expertise facilitated the development of this webpage and video.
This work is supported by the NCI, grant number 3P30CA023108-40S4