What do you need to know about colon cancer screening?
- Krishnamohan,MD
- May 20, 2018
- 5 min read
Colorectal cancer is the second leading cause of cancer-related deaths in the United States. It is the third most common cancer in men and in women. Colorectal cancer develops in the colon or rectum. The primary goal of colon cancer screening is to identify colon cancers or precancerous growths early and to prevent deaths from colon cancer.
Adults should undergo colon cancer screening beginning at age 50 or earlier, depending upon their risk of developing colorectal cancer. You do not need screening if you are above 75 years of age. If you have a family history of colon cancer screening should begin 10 years prior to the onset of colon cancer in the family or at age 50 whichever comes first. If you have a condition called Ulcerative Colitis, it puts you at a high risk of developing colon cancer. screening for colon cancer should begin with an initial colonoscopy eight year after the onset of pancolitis and 12 to 15 years after the onset of left-sided disease; follow-up colonoscopy should be repeated every two to three years. Several tests are available for colon cancer screening, each of which has advantages and disadvantages. The optimal screening test depends upon your preferences and your risk of developing colon cancer.
Who is at increased risk of developing colon cancer?
Family history of colorectal cancer - People who have one first-degree relative (parent, brother, sister, or child) with colorectal cancer or adenomatous polyps at a young age (before the age of 60 years), or two first-degree relatives diagnosed at any age. People with a second-degree relative (grandparent, aunt, or uncle) or third-degree relative (great-grandparent or cousin) with colorectal cancer are considered to have an average risk of colorectal cancer.
People with family history of familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (HNPCC).
People with inflammatory bowel disease such as ulcerative colitis or crohn's disease are at higher risk of developing colon cancer
People with prior colorectal cancer or polyps
Lifestyle factors – Several lifestyle factors increase the risk of colorectal cancer, including a diet high in fat and red or processed meat and low in fiber, sedentary lifestyle, Cigarette smoking, Alcohol use and Obesity
Protective lifestyle factors to reduce the risk of colon cancer
Regular physical activity
Regular use of Aspirin (It showed benefit only when patients were able to take aspirin for 10 years)
Use of NSAIDS such as Motrin / Advil (however risk of adverse events from these medications are greater than the benefits)
Diet high in fruits and vegetables
Increased vitamin B6 and folate intake
Increased Vitamin D, calcium and dairy intake
Fish or omega 3 fatty acid Consumption
Calcium supplementation reduces the risk of developing colon cancer
Avoid smoking
Low BMI
Reduction in red meat consumption is associated with less risk of developing colon cancer
Observational studies have found conflicting evidence on the relationship between coffee consumption and reduced risk of Colorectal cancer
Screening methods for Colorectal cancer
Colonoscopy
Colonoscopy is a procedure done to visualize your colon directly and to take any samples if needed. Your doctor will ask you to drink a liquid the day before the test to clean out your colon. On the day of the test, you will be given a medicine to help you relax. Then the colorectal surgeon will put a tube with a camera attached to it into your anus and advance it into your colon. The tube also has tiny tools on the end, which will allow your doctor to remove any polyps or abnormal tissues. Polyps and tissues that were removed from your colon is then sent to the pathology lab to check for signs of cancer.
Advantages of this test – This is the most accurate test for colon cancer screening. When suspicious polyps were found it can be removed right away and can be sent to the lab for further investigation. Colonoscopy will be required if you do any other screening test and if they show suspicious polyps.
Disadvantages of this test – Prepping for colonoscopy is not something patients enjoy doing. Colonoscopy can also cause bleeding or tear the inside of the colon, but this only happens in 1 out of 1,000 people.
Sigmoidoscopy
A sigmoidoscopy is similar to a colonoscopy. The difference is that this test looks only at the last part of the colon whereas colonoscopy looks at the whole colon. You need to clean your colon with enema prior to the procedure however it is not as bad as prepping for colonoscopy.
Advantages of this test – Colon cancers are most commonly found in the last part of the colon. Sigmoidoscopy can find polyps and cancers in the rectum and the last part of the colon. If polyps are found, they can be removed right away.
Disadvatages – In about 2 out of 10,000 people, sigmoidoscopy tears the inside of the colon. The test also can't find polyps or cancers that are in the part of the colon the test does not view
Stool test - FOBT
Stool tests most commonly check for blood in samples of stool. Cancers and polyps can bleed, and if they bleed around the time you do the stool test, then blood will show up on the test. The test can find even small amounts of blood that you can't see in your stool. Other less serious conditions can also cause small amounts of blood in the stool, and that will show up in this test.
Advantages of this test – This test does not involve cleaning out the colon or having any procedures.
Disadvantages – Stool tests are less likely to find polyps than other screening tests. These tests also often come up abnormal even in people who do not have cancer. If a stool test shows something abnormal, doctors usually follow up with a colonoscopy.
Fecal immunochemical tests (FIT) for blood
FIT test is more specific than regular stool blood test. FIT detects only human globin and therefore does not detect upper gastrointestinal bleeding (since the globin is digested in transit). Additionally, foods with peroxidase activity do not produce a positive reaction. Annual testing with FIT, alone or in combination with sigmoidoscopy every 10 years, is one of several options for screening of colon cancer.
Fecal DNA test
Genetic mutations and epigenetic changes acquired during carcinogenesis can be detected in the stool from DNA shed by colorectal neoplasms. This test can be performed every 3 years instead of every year like other stool test. Further research needs to be done prior to understanding the accuracy and benefits of this test
How often should I be screened?
It depends on your risk of colon cancer and which test you have. People who have a high risk of colon cancer often need to be tested more often and should have a colonoscopy.
If you are not at high risk of developing colon cancer then you could follow either
●Colonoscopy every 10 years
●Sigmoidoscopy every 5 to 10 years
●Stool testing for blood or FIT test once a year
●Stool DNA testing every 3 years (but doctors are not yet sure of the best time frame)
Colorectal cancer resource links :
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