COLORECTAL CANCER SCREENING
An average person has a 5 percent lifetime risk of developing colorectal cancer.
Most colorectal cancers develop from precancerous adenomatous polyps. A small percentage of these polyps become cancerous. This progression takes at least 10 years in most people. Early detection of lesions increases the chances of successful treatment and decreases the chance of dying as a result of the cancer.
Colon cancer screening tests work by detecting polyps or by finding early stage cancers. Regular screening for and removal of polyps can reduce a person's risk of developing colorectal cancer by up to 90 percent.
RISK FACTORS
Family history of colorectal cancer -Colorectal cancer in a family member increases an individual's risk of cancer, especially if the family member is a first degree relative (a parent, brother or sister, or child), if several family members are affected, or if the cancers have occurred at an early age (before age 55 years)
Prior colorectal cancer or polyps
Increasing age -90% of cancers occur in people older than 50 years of age. Risk increases with age throughout life.
Lifestyle factors -A diet high in fat and red meat and low in fiber , sedentary lifestyle, cigarette smoking
Familial adenomatous polyposis (FAP) is an uncommon inherited condition that increases a person's risk of colorectal cancer. Nearly 100 percent of people with this condition will develop colorectal cancer during their lifetime, and most of these cancers occur before the age of 50 years.
Hereditary nonpolyposis colon cancer (HNPCC) is another inherited condition associated with an increased risk of colorectal cancer. About 70 percent of people with HNPCC will experience colorectal cancer by the age of 65. Cancer also tends to occur at younger ages and in the part of the colon on the right side of the body.HNPCC is suspected in those with a strong family history of colon cancer; several family members from different generations may have been affected, some of whom developed the cancer relatively early in life. People with HNPCC are also at risk for other types of cancer, including cancer of the uterus, stomach, bladder, kidney, and ovary.
Inflammatory bowel disease- People with Crohn's disease of the colon or ulcerative colitis have an increased risk of colorectal cancer. The degree of increased risk depends upon the amount of inflamed colon and the duration of disease; pancolitis (inflammation of the entire colon) and colitis of 10 years' duration or longer are associated with the greatest risk for colorectal cancer. The risk of colon cancer is not increased in people with irritable bowel disease.
Factors that may decrease risk include a high calcium diet ( at least 1000 mg of calcium daily, either through diet or by taking a calcium supplement)
SCREENING TESTS - tests that can detect cancers at an early treatable stage (eg, stool tests), and tests that also detect pre-cancerous polyps (adenomas) and can lead to cancer prevention.
Stool tests - Colorectal cancers often bleed, releasing microscopic amounts of blood and abnormal DNA into the stool. Stool tests can detect blood or abnormal DNA makers. Guaiac testing, when performed once per year, can reduce the risk of dying from colorectal cancer by at least one-third.
Disadvantages -Guaiac testing is less likely to detect polyps than other screening tests.
If the stool test is positive, the entire colon should be examined with colonoscopy
Colonoscopy
Procedure - Colonoscopy requires that the patient prepare by cleaning out the entire colon and rectum by consuming a liquid medication that causes diarrhea temporarily. After gentle sedation, a thin, lighted tube is used to directly view the lining of the rectum and the entire colon.
Advantages-Only test that can “remove” polyps in the whole colon
Disadvantages - Colonoscopy leads to serious bleeding or a tear of the intestinal wall in about 1 in 1,000 people.
There is also the possibility of missing polyps or cancer .
CT colonography
Procedure - Computed tomography colonography (CTC) is a test that uses a CT scanner to take images of the entire bowel to determine if polyps or cancers are present
Advantages -It does not require sedation and is non-invasive
The entire bowel can be examined, and polyps can be detected about as well as with traditional colonoscopy.
Disadvantages -CTC requires a bowel prep to clean out the colon.
If an abnormal area is found with CTC, a traditional colonoscopy will be needed to remove a polyp ot biopsy a mass/cancer
Incidental findings detected on CTC will require further testing.
Double contrast Barium enema and flexible sigmoidoscopy are also used for screening although less commonly than other modalities
PLEASE DISCUSS THE APPROPRIATE SCREENING MODALITY WITH YOUR PHYSICIAN
Average risk of colorectal cancer
People with an average risk of colorectal cancer should begin screening at age 50.
Increased risk 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, should begin screening for colon cancer earlier, typically at age 40, or 10 years younger than the earliest diagnosis in their family, whichever comes first. Screening usually includes colonoscopy, which should be repeated every five years.
People who have one first-degree relative (parent, brother, sister, or child) who has experienced colorectal cancer or adenomatous polyps at age 60 or later, or two or more second degree relatives (grandparent, aunt, uncle) with colorectal cancer should begin screening at age 40, and screening should be repeated as for average risk people.
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
Familial adenomatous polyposis — People with a family history of familial adenomatous polyposis should consider genetic counseling and genetic testing to determine if they carry the affected gene. People who carry the gene or do not know if they carry the gene should begin screening with sigmoidoscopy once every year, beginning at puberty.Colectomy is the only way to prevent colorectal cancer in people with FAP.
Hereditary nonpolyposis colon cancer — People with a family history of hereditary nonpolyposis colon cancer should consider genetic counseling and genetic testing to determine if they carry the affected gene. People who carry the gene or who do not know if they carry the gene should be screened with colonoscopy because HNPCC is associated with cancers of the right-sided colon (which cannot be seen during sigmoidoscopy).
Depending upon the family history and what is found, colonoscopy is usually repeated every one to two years between age 20 and 30 years, and every year after age 40
Inflammatory bowel disease — In people with ulcerative colitis or Crohn's disease of the colon, the optimal screening plan depends upon the amount of colon affected and the duration of the disease.
For more information please see
www.nci.nih.gov
www.cancer.net/portal/site/patient
www.nccn.org/patients/patient_gls.asp
www.cancer.org
www.nlm.nih.gov/medlineplus/healthtopics.html
www.gastro.org
www.acg.gi.org