Here you can find out more about a colon cancer screening and surveillance.
The colon is a long, muscular tube that receives undigested food from the small intestine, removes water from the undigested food, stores it and then finally eliminates it from the body through bowel movements. The last part of the colon adjacent to the anus is the rectum.
Cancer of the colon and rectum (also known as colorectal cancer) is a malignant tumor arising from the inner wall of the large intestine and it invades nearby tissue and spread to other parts of the body.
Polyps are benign tumors of the colon. They do not invade nearby tissue or spread to other parts of the body, but they must remove during colonoscopy because they can become malignant (cancerous) over time.
Metastasis is the process when colon cancer spreads to distant organs and the new tumors are called metastases and when they occur, complete cure of the cancer is unlikely but colorectal cancer is preventable and curable.
Usually, polyps and early cancers produce no symptoms, so it is important to do screening and surveillance for colon cancer in patients without symptoms or signs of the polyps or cancer.
Recommended screening tests for individuals with average risk of colon cancer are a fecal occult blood test and flexible sigmoidoscopy examination because these tests can detect and remove precancerous polyps and identify early cancers in order to decrease mortality from colorectal cancer.
- Fecal occult blood test (FOBT) is a test performed on samples of stool in order to detect occult blood (blood that is not visible to the naked eye) in the otherwise normal-colored stool. Usually, it is a result of slow bleeding from inside the upper of the lower gastrointestinal tract and it does not change the color of the stool.
- Flexible sigmoidoscopy is a procedure during which lower (sigmoid) colon and rectum are being examined with flexible sigmoidoscope – flexible tube 60 cm long and about the thickness of your little finger. The sigmoidoscope is inserted gently into the anus and advanced slowly into the rectum and the lower colon under direct vision on a TV monitor. This procedure is a shorter version of a colonoscopy and approximately 50% of colorectal cancers and polyps are found to be within the reach of a flexible sigmoidoscope. It is recommended at the age 50 and every 3-5 years thereafter.
- Colonoscopy is an examination of the colon (large intestine) and rectum, using an instrument called a colonoscope – four-foot long, flexible tube about the thickness of a finger with a camera and a source of light at its tip. It is recommended at the age 50 and every 7-10 years. During a colonoscopy, the entire colon is examined and approximately 50% of colon polyps are found in the upper colon, beyond the reach of flexible sigmoidoscopy.
- Virtual colonoscopy is an alternative to colonoscopy and it is a technique that uses computerized tomography (CT) scanning to obtain images of the colon that are similar to the views of the colon obtained by direct observation through colonoscopy. It can find polyps "hiding" behind folds that occasionally are missed by colonoscopy, but it has several limitations: it has difficulty identifying small polyps (less than 5 mm in size) that are easily seen at colonoscopy and flat cancers or premalignant lesions that are not protruding, that is, are not polyp-like. Also, virtual colonoscopy does not allow removal of polyps that are found and exposes individuals to a moderate amount of radiation. Because of these limitations, virtual colonoscopy has not replaced colonoscopy.
- Air contrast (double contrast barium enema) is an X-ray procedure used to define the anatomy of the large intestine (colon) and the rectum. It is not as accurate as colonoscopy or, perhaps, virtual colonoscopy in detecting small polyps or cancers so it is not widely used for colon cancer or polyp screening.
Periodical colonoscopies are recommended to:
Individuals with higher than average risk of colon cancer because of:
- A family history of colon cancer
- A history of chronic ulcerative colitis
- A history of colon polyps or cancer
- Familial adenomatous polyposis (FAP) – hereditary colon cancer syndrome in which the affected family members develop large numbers (hundreds, sometimes thousands) of colon polyps starting in their teens
- Attenuated familial adenomatous polyposis (AFAP) – milder version of FAP
- Hereditary nonpolyposis colon cancer (HNPCC) – hereditary cancer syndrome in which affected family members tend to develop colon cancers, usually in the right colon, in their 30’s to 40’s
- MYH polyposis syndrome – hereditary cancer syndrome in which affected patient typically develop 10-100 polyps during their 40's and are at high risk for developing colon cancer
- Patients with a history of colon polyps
- Patients with history of colorectal cancer (also annual testing of stool for occult blood is recommended)
- Patients with ulcerative colitis, because the risk of developing colon cancer is proportional to the duration of disease and to the extent of colon involved by colitis.
Genetic counseling and then another testing should be considered for individuals as well as their family members when there are:
- Individuals in the family with early onset of colon cancer, before age 50
- Individuals in the family with numerous colon polyps
- Families with members with numerous colon polyps
- Families with members having colon cancers at young ages
- Families in which multiple members have colon cancer
- Families with members having certain non-colon cancers such as cancers of the uterus, thyroid, urethras, ovaries, small intestine, etc.
Genetic testing is done after counseling first with the person who has the disease and if genetic testing of this person reveals a mutation responsible for a hereditary colon cancer syndrome, then other family members can be tested for the same mutation.
If the genetic tests are positive for hereditary colon cancer syndromes, it is recommended that a person starts with colon screening very early, for example, patients with FAP should have annual flexible sigmoidoscopy starting at age 12, patients with AFAP should have annual colonoscopies starting at age 25, and patients with HNPCC should have colonoscopies beginning at age 25 (or 10 years younger than the earliest colon cancer diagnosed in the family, whichever is earlier).