Colon Cancer Screening: A Life Saving Tool
By Rhonda Mann
Beth Israel Deaconess Medical Center Staff
Dr. Helen Shields has found many cancers lurking inside colons over the years. But when a colleague and friend in her late fifties came to her with symptoms and a strong family history of the disease, she was particularly troubled.
"Her mother had died of colon cancer in her early fifties," recalls
Dr. Shields, a gastroenterologist at Beth Israel Deaconess Medical Center and Chairman of the Colorectal Cancer Advisory Committee at
Harvard University's Risk Management Foundation. "She said to me, I know I should have come sooner to get checked, but I couldn't bring myself to do it."
One in eighteen people will develop colon cancer in their life-time -- and screening is key to finding growths early when they are most treatable. Yet fewer than 50 percent of those who should be screened, are screened.
"Data suggests that colon cancer is not screened with the same intensity as breast, cervical cancer or prostate cancer," she says.
For some, the hesitancy is the nature of the gold-standard test-- the colonoscopy. Doctors insert a special scope into the rectum, searching the 5 foot long colon for growths. The day before the test, patients drink a solution that cleans out their system, so they need to have a bathroom nearby. Doctors agree that while they do everything to make the exam comfortable, it's not something most patients look forward to.
"There are some patients who just aren't willing to have a colonoscopy," explains Shields. "For those patients, there are other tests. We'd rather have you do something for colon cancer screening than nothing."
Those tests include a flexible sigmoidoscopy, which examines the last third of the colon and requires no sedation, allowing patients to return to work immediately afterwards. Each patient with a polyp on flexible sigmoidoscopy should have a complete colonoscopy to remove the polyp and search for others.
Another test, the fecal occult blood test, involves a sample of stool placed on a card for detection of blood in the stool. All positive tests for blood in the stool need to be followed by a colonoscopy to exclude colon cancer or polyps as the cause of bleeding.
The conventional stool tests for occult blood tests pick up about 24% of colon cancers present in the colon. Other stool-based tests are now available which focus on an immunochemical detection, using antibodies to human hemoglobin, of blood in the stool. These tests are more sensitive at finding cancers but are also more expensive. The immunochemical tests have not been widely adopted by hospitals and primary care physicians because of the extra expense.
Shields says combined, the flexible sigmoidoscopy and the conventional fecal occult blood test pick up approximately 75 percent of cancers compared to a 95 percent detection rate with colonoscopy.
Shields notes that researchers are working on newer ways of detecting colon cancers, such as virtual colonoscopy, where a CAT scan and 3D technology provide a virtual journey through the colon. However, just last month, Medicare announced that the government will not pay for virtual colonoscopy as a colon cancer screening tool for patients over 65 years of age. Medicare cited insufficient evidence to conclude that virtual colonoscopy improves outcomes in Medicare beneficiaries.
Physicians are also evaluating stool DNA tests to detect mutations in the colonic cells shed into the stool that may indicate the presence of cancer in the colon. While somewhat expensive, they do offer another alternative for patients unwilling to undergo invasive testing with colonoscopy or flexible sigmoidoscopy.
Additional studies are being performed with a capsule that contains a tiny camera -when swallowed it transmits images as it makes its way through the digestive tract. This technology is not ready as a screening tool at present.
"In the future, we may have better, less invasive screening tests," says Shields. "But right now, colonoscopy is the best technology we have to both find cancers and find and remove precancerous polyps. I recommend it as the optimal screening method."
Everyone age 50 and older should be screened. For those at higher risk, screening may need to begin before the age of 50. Moderate and high risk groups include those who have a family history of colon cancer, especially if the relative developed the cancer before the age of 60, or a family history of polyps; those who themselves have had polyps or colon cancer; and those with longstanding Crohn's disease or ulcerative colitis.
"Also, anyone with rectal bleeding should talk to their doctor about getting screened," says Shields. "Sometimes people assume it's just hemorrhoids, but it can be a sign that there is a growth where there shouldn't be."
Screening does work, says Dr. Shields, as is evidenced by the most recent government statistics. For the first time, the number of deaths from colon cancer has significantly declined in the United States.
Still, Dr. Shields says there is more work to do - motivating those who should come in - like her colleague and friend who died just months after being diagnosed.
"Here was someone who was at high risk and knew she should have had this test much, much earlier," says Shields. "We can save people...but first we have to know the cancer exists."
Above content provided by Beth Israel Deaconess Medical Center
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Posted March 2009