Colorectal cancer is the third most common cancer in adults and the second leading cause of cancer deaths in men and women in the United States. Cancer of the colon and rectum is both preventable and treatable if detected early. Studies show that regular screening could prevent one-third of colorectal cancer deaths in the U.S.
Screening tests that look for and remove polyps and lesions in the colon can prevent colorectal cancer. These are found most often in people 50 years of age and older, so experts recommend universal screening of average risk people in this age group. However, if you have one or more risk factors for colon cancer, described below, you should talk to your doctor about screening at a younger age. Those risk factors could include hereditary conditions, family history of colon cancer, and lifestyle.
The exact causes of colon and rectal cancer are not known, but risk appears to be associated with genetic, dietary, and lifestyle factors. Earlier, more frequent screening is appropriate at a younger age for those who have risk factors, often beginning at age 40. Screening can begin even earlier in some cases.
- Average risk: People age 50 and older with no known risk factors.
- Increased risk: If you have a family history of colorectal cancer or adenomatous polyps—a specific type of polyp associated with higher risk of colorectal cancer. Most of these cancers occur in people without a family history of colorectal cancer. Still, as many as 1 in 5 people who develop colorectal cancer have other family members who have been affected by this disease.
Specifically, if you have a first-degree relative (parents, siblings or children) who had colorectal cancer or adenomatous polyps before age 60, or two or more first-degree relatives that had either of these findings at any age, you have increased risk for colorectal cancer. The risk is about doubled in those with one affected first-degree relative. It is even higher if the first-degree relative is diagnosed at a young age, or if more than one first-degree relative is affected.
You may also be at increased risk for colorectal cancer if you have been diagnosed with colon cancer in the past or if you have had a history of polyps on a prior colonoscopy.
- High risk: If you have a genetic syndrome such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC), or if you are at an increased risk of HNPCC based on your family history, you are at high risk for colorectal cancer. If you have inflammatory bowel disease, including chronic ulcerative colitis or Crohn's disease, you are also in the high-risk category.
According to the Centers for Disease Control and Prevention (CDC), lifestyle factors that may contribute to increased risk for colon cancer include lack of regular physical activity, low fruit and vegetable intake, a low-fiber and high-fat diet, obesity, alcohol consumption, and smoking.
Types of Tests Used for Screening
Recommendations for colon cancer screening include laboratory tests performed on your stool samples to detect existing cancers and imaging tests on the inside of your colon that can detect pre-cancerous polyps and existing cancers.
- Laboratory tests find telltale blood or DNA—signs that cancer is present—in a stool sample. The three types of lab tests are:
- Imaging procedures show abnormalities—polyps and less conspicuous flat lesions—on the empty colon's lining.
- Two of these procedures use a scope with a video camera: colonoscopy views the entire length of the colon, and flexible sigmoidoscopy views the lower third. These two approaches to screening are also able to remove any polyps that are found and allow them to be tested for the presence of cancer cells.
- The other two procedures use x-rays: virtual colonoscopy—a computed tomography (CT) scan—combines many cross-sectional images into 2-D and 3-D views of the colon, and a double-contrast barium enema (DCBE) provides x-ray views of lumps, polyps, and abnormalities in the outline of the colon. However, these approaches only allow visualization of the polyps. To remove the polyps would require a follow-up colonoscopy or flexible sigmoidoscopy.
Colonoscopy is the most accurate and thorough test, but also the most costly and invasive. However, it is especially appropriate for those with risk factors. Stool sample testing and sigmoidoscopy are easier than colonoscopy, but not as accurate. Stool testing and sigmoidoscopy are best used together.
Your doctor can help you assess your individual risk factors and determine if you should begin screening before age 50, and what tests are appropriate based on your risks. As the CDC notes, any of the recommended tests is better than no test.
Several health organizations have their own colon cancer screening recommendations. While they may differ on which tests to use and how often, they each support screening for colon cancer. In March 2008, screening guidelines for the early detection of pre-cancerous polyps and colon cancer were released jointly by the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. These guidelines provide the most comprehensive screening guidelines for people who are at increased risk for colon cancer and thus candidates for screening before age 50. If you are at increased or high risk for colorectal cancer, your health care provider can help you assess the best combinations of preventive tests and how frequently you should have them.
- According to the joint guidelines, if you have a family history of colorectal cancer or adenomatous polyps in any first-degree relative (parents, siblings or children) before age 60, or in two or more first-degree relatives at any age (if not a hereditary syndrome), screening with colonoscopy should begin at age 40.
If you have a family history of colorectal cancer or adenomatous polyps in any first-degree relative who was 60 or older, or in at least two second-degree relatives at any age, they recommend screening options that are the same as those offered to someone of average risk.
Inflammatory bowel disease: the guidelines recommend that screening begin 8 years after the onset of the disease.
Hereditary non-polyposis colon cancer (HNPCC): the guidelines recommend that screening begin when you are 20 to 25 years old, or 10 years before the youngest case in the immediate family.
Familial adenomatous polyposis (FAP) diagnosed by genetic testing, or suspected FAP without genetic testing: ACS recommends that screening begin at 10 to 12 years of age.
- According to the U.S. Preventive Services Task Force (USPSTF), people whose first-degree relatives had colorectal adenomas or cancer can follow the same recommendations as those for someone at average risk. However, for people with first-degree relatives who developed cancer at a younger age or people with multiple affected first-degree relatives, the USPSTF advises screening before age 50.
Some groups, such as the American College of Gastroenterology, recommend that people of African descent begin testing at age 45. However, the USPSTF states that its recommendations for average risk individuals are intended to apply to all ethnic and racial groups.
Talk to your health care provider about the screening tests recommended for you. Some employers, health plans, and health care providers offer decision aids.
Also, don't neglect the protection of getting re-tested at the interval recommended by your health care provider. Ask or sign up for a mailed or e-mailed reminder (see Links below), or mark your calendar or date book.
College of American Pathologists: MyHealthTestReminder.com - Colon Cancer Screenings
Your Disease Risk: Colon cancer risk calculator
Centers for Disease Control and Prevention: Colorectal (Colon) Cancer
Sources Used in Current Review
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