Colorectal Cancer Screening
James Metz, MD
Abramson Cancer Center of the University of Pennsylvania
Last Modified: November 1, 2001
It is estimated that more than 131,000 Americans will develop colon or rectal cancer
in 1998. It is the second most common cause of death from cancer in the United States. Colorectal cancer can be treated effectively when it is discovered at an early stage of disease.
There are a number of risk factors associated with the development of colorectal cancer. Hereditary colon polyps, cancer family syndromes,and a history of colorectal cancer in a first-degree relative all place the individual at a higher risk. A personal history of adenomas and colonpolyps, previous colorectal cancer, or inflammatory bowel disease places the individual at higher risk. However, less than 1/3 of patientsdiagnosed with colorectal cancer have high-risk features. There is an increased risk of developing colorectal cancer with increasing age. Forthis reason, it is recommended all individuals over the age of 50 participate in colorectal cancer screening.
There are a number of screening tests utilized for colorectal cancer:
- Digital Rectal Examination: The physician inserts a gloved finger into the rectum and feels for any abnormalities. If no blood is visible on thegloved finger, fecal occult blood testing is performed (see below). To date, there has not been significant evidence that the rectal examinationhas had any effect on mortality when used alone as a screening test.
- Fecal Occult Blood Testing: Special cards are utilized to test for occult blood (blood not seen by the naked eye). Patients can place a smallsample of feces on the card at home or the physician can place a sample on the card after a digital rectal examination. A special chemical is usedby the lab to determine if blood is present. It should be noted many things could cause a positive occult blood test. If you have a positive test,further studies are warranted. Fecal occult blood testing on an annual or biannual basis for individual 45-80 years of age has been shown todecrease mortality from colorectal cancer.
- Sigmoidoscopy: A sigmoidoscope is a thin tube with a light at the end, which is placed into the rectum. It can evaluate the distal colon and therectum for polyps, tumors, and other abnormalities. Regular screening in individuals over 50 years of age may decrease mortality fromcolorectal cancer. There has been significant controversy over the optimal screening interval.
- Colonoscopy: The colonoscope is much longer than a sigmoidoscope so that the entire colon can be evaluated. Patients are usually sedatedfor a colonoscopy procedure. A colonoscopy may be recommended for patients who are at high risk for colorectal cancer, have abnormalitieson a sigmoidoscopy, or have unexplained fecal occult blood.
- Barium Enema: A barium enema is a radiologic study of the colon and rectum. Barium is contrast material that is given by enema prior totaking X-rays. This allows the colon and rectum to be visualized and abnormalities can be evaluated. The patient is placed on a table thatmoves so the contrast can be followed through the bowel.
The American Cancer Society recommends three courses of action beginning at the age of 50, from which the patient and physician can choosefor screening. These include:
- Annual fecal occult blood tests, together with a flexible sigmoidoscopy and digital rectal examination every 5 years.
- Colonoscopy with digital rectal examination every 10 years
- Double contrast barium enema with digital rectal examination every 5-10 years