Screening for Colorectal Cancer

Options, old and new, are making diagnosis easier and more accurate.

By Jennifer M. Gangloff

Even After Robin Lindley’s elderly mother was diagnosed with colon cancer, he resisted his family’s suggestions that he get screened for the disease himself. He was young, after all, only 47, and had no symptoms.

But four months later, in late November 1996, Lindley relented and had a colonoscopy. Two weeks after that, he was in surgery to remove a tennis ball-sized tumor and facing a year of chemotherapy for stage 3 colon cancer.
“If I hadn’t gotten that colonoscopy, it would have been curtains for me,” says Lindley, of Seattle. “Here I had colon cancer and I wasn’t even going to get the test.”

Like Lindley, many Americans—more than half—put off recommended colorectal cancer screenings, says internist Laura C. Seeff, MD, a medical officer for the Centers for Disease Control and Prevention. That’s mainly because they’re not aware of the need and because their doctors may not routinely recommend screening, she says.

That’s also the reason colorectal cancer remains the second leading cause of cancer-related deaths in the United States. An estimated 146,000 Americans will be diagnosed with colon or rectal cancer in 2004, with 56,000 deaths. “With regular screening, we can prevent at least one-third of colorectal cancer deaths,” Dr. Seeff says.

Screening can prevent colorectal cancer by finding and removing adenomatous polyps that may turn malignant or detecting cancer in its earliest stage, when the cure rate is as high as 90 percent.

Traditional Screening Options

Here are the five traditional colorectal cancer screening methods, along with the recommended testing frequency for those over age 50 and at average risk:

Fecal occult blood test (FOBT): This checks for invisible blood in the stool, which may result from bleeding masses. Using a home kit, you collect stool smears and send them to your doctor or a lab for analysis. This test is safe and relatively convenient. But it can’t detect a tumor that’s not bleeding. In addition, results may be skewed by foods such as red meats, supplements such as vitamin C or medications such as aspirin or NSAIDs, causing the test to indicate blood is present when it actually isn’t (a false-positive) or that it isn’t present when it actually is (a false-negative). Other tests, including colonoscopy, may be necessary if results indicate the presence of blood.
Frequency: Annual

Flexible sigmoidoscopy: This examines the rectum and lower portion of the colon using a sigmoidoscope, a thin, flexible tube typically with a tiny video camera to display images. A biopsy of suspicious lesions can be obtained at the same time. It can be done in your doctor’s office or a hospital in about 10 minutes, without sedation. Drawbacks to the test are abdominal pain and preprocedure bowel-cleansing enemas. The tube is long enough to examine only about the lower 2 feet of the colon, so masses higher up will be missed—perhaps as many as half. Complications are rare.
Frequency: Every five years

Combined FOBT and sigmoidoscopy: To overcome some of the limitations of the FOBT and sigmoidoscopy, the two may be performed together. The FOBT should be done first since a positive result would likely necessitate a full colonoscopy.
Frequency: Every five years

Double-contrast barium enema (DCBE): This procedure, also called an air-contrast barium enema, takes a series of X-rays of the colon and rectum to detect abnormalities. Barium sulfate, a chalky liquid, is infused into the colon, along with air. The procedure takes about 30 to 60 minutes and you must move into various positions for the X-rays. Test preparation includes cleansing the bowels with laxatives and enemas. Sedation isn’t required, but you may experience some discomfort. Serious complications, such as bowel perforation, are rare. Lesions or masses must be further evaluated or removed by colonoscopy. DCBE may miss small polyps.
Frequency: Every five years

Colonoscopy: Considered the gold standard, colonoscopy uses a long, flexible tube to examine the entire 5-foot colon. Polyps can be biopsied or removed during the procedure. Preparation includes dietary restrictions and bowel-cleansing laxatives. The procedure takes about 30 minutes, with a recovery of a few hours because of sedation. There’s a small risk of bowel perforation and anesthesia complications. And although colonoscopy can detect polyps or tumors missed by FOBT or sigmoidoscopy, this exam is also not 100 percent accurate and may overlook some lesions. Important to note is the recent report in the Annals of Internal Medicine that found doctors are performing too many follow-up, or surveillance, colonoscopies on patients who had low-risk colon polyps removed.
Frequency: Every 10 years

Evolving Technologies

New screening methods are also being developed, with an eye toward improved accuracy, convenience, affordability and accessibility. The most promising newcomers:

Fecal DNA testing: Ultra-sensitive lab tests can detect changes in the DNA of cells shed from polyps or cancers into stool, without the need for invasive scopes (see illustration). Positive results would trigger colonoscopy for further evaluation. The DNA test requires no special diet, medication changes or bowel preparation, says David Ahlquist, MD, professor of medicine and consultant in gastroenterology at the Mayo Clinic in Rochester, Minnesota.

“It’s in its early stages and we need to hold judgment until we have the results of larger studies,” Dr. Ahlquist says. “But the user-friendly features of this approach could lead to improved screening participation.”

While DNA stool testing is available commercially, definitive data are not yet out and insurers don ’t cover the procedure.

Virtual colonoscopy: Technically known as computed tomographic (CT) colonography, this procedure takes a series of X-ray images of the colon and rectum and turns them into multidimensional views with computer software. Although this is a noninvasive procedure that doesn’t involve a scope, air must be pumped into the colon to distend it and you must drink an oral contrast substance. Preparation for the procedure is similar to that for colonoscopy. It requires no sedation and is relatively safe. However, if polyps are found, they must be removed by a conventional colonoscopy.

Insurance coverage varies, although insurers are more likely to cover the test for someone with potential symptoms of colorectal cancer, such as rectal bleeding, abdominal pain and changes in bowel habits.

Its use remains controversial, though, and some critics contend virtual colonoscopy misses potentially cancerous small polyps. Still, Joseph Ferrucci, MD, professor and chairman emeritus in the Department of Radiology at Boston Medical Center/Boston University School of Medicine, is a strong advocate and says the newest versions of virtual colonoscopy are at least as good as conventional colonoscopy.

“We know those small polyps aren’t significant, and we can’t drive everyone crazy by reporting all of the little pimples and dimples in the human body,” Dr. Ferrucci says. “It has tremendous results when performed by people who are properly trained and experienced.”

Remaining Vigilant

There’s no one best option for colorectal cancer screening. Your doctor can help you decide which method and schedule is best for you. You may need more frequent or earlier screening if you have a personal or family history of certain cancers or genetic disorders.

Regardless of what screening method you opt for, also pay attention to potential signs and symptoms of colorectal cancer.

For Dusty Weaver of Conway, Arkansas, it was dark, tarry blood that appeared in his stool in August 2000, when he was just 43. Within days, he had his stool checked for blood, and then a full colonoscopy when the results were positive. He was soon diagnosed with stage 2 rectal cancer, and surgery, chemotherapy and radiation followed. The cancer has not recurred, and Weaver continues to get colonoscopies every two years.

“The typical person doesn’t know anything about colon cancer and doesn’t want to know anything,” Weaver says. “If they see blood, they think maybe it’ll go away. A colonoscopy isn’t as bad as it sounds. I’ve had three and I’m still here. In fact, I’m still here because I had them.”