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Make an Individualized Choice for Colon Cancer Screening: Experts outline options for how, when, and how frequently to undergo screening, but you have to choose what's best for you.

James Church, MD, says every patient he sees with colorectal cancer represents a missed opportunity for prevention. Unlike other common cancers, colorectal cancer can be prevented with screening--namely, with colonoscopy and removal of precancerous colorectal polyps (polypectomy).

"Every colorectal cancer arises in a precancerous polyp, and the time for cancer to develop averages about 10 years," says Dr. Church, with Cleveland Clinic's Department of Colorectal Surgery. "This is a decent window of opportunity to remove the precancerous polyp, thus preventing cancer. Finding precancerous polyps means screening, and removal of the polyps means colonoscopy. There are alternatives to screening colonoscopy, however."

Recent guidelines from the American Cancer Society (ACS) outline your screening options. They also call for screening in average-risk individuals to begin at age 45, instead of age 50, and that if you're over age 75, you should talk to your physician about your need for continued screening. Yet, as Dr. Church emphasizes, decisions about colorectal cancer screening remain highly individualized.

Visualizing the Colon

A colonoscopy allows your physician to view your entire colon and remove precancerous colorectal polyps (adenomas) before they develop into cancer. Colonoscopy is the most invasive screening option and requires bowel preparation, which most patients find onerous. However, when done by a skilled operator, it's the best option, Dr. Church says, and it's the preferred choice of the U.S. Multi-Society Task Force (USMSTF) on Colorectal Cancer Screening.

"If a patient asks what's the best way to keep from getting colon cancer, I would say the only way is to get a colonoscopy by someone who's good and can detect polyps," he says. "We find lots of polyps, we take them out, and we prevent lots of cancers."

The ACS also recommends flexible sigmoidoscopy (flex sig) and computed tomography (CT) colonography (virtual colonoscopy) as other options that visualize the colon. Like colonoscopy, flex sig uses a flexible scope, but it views only the rectum and left side of the colon. Still, research suggests it can reduce colorectal cancer incidence and mortality.

CT colonography uses CT imaging to view the colon and rectum. Although non-invasive, it's associated with a fairly high rate of false-positive results, Dr. Church says, and it requires bowel cleansing and inflation of the colon with air. "It's still used for patients who can't or won't get colonoscopy," he says, "but it's pretty much dropped off the scene."

Another option for patients unable to complete an optical colonoscopy is capsule colonoscopy (PillCam Colon[TM]), in which you swallow a pill containing a camera that photographs your colon and transmits images to an external device. While the USMSTF includes capsule colonoscopy as a "third-tier" screening option that can be offered every five years for average-risk patients, the ACS guidelines do not recommend it for routine screening.

Stool-Based Tests

Home-based assays that check for blood in your stool, such as the high-sensitivity fecal immunochemical (FIT) and high-sensitivity guaiac-based fecal occult blood test (g-FOBT), can reduce death rates from colorectal cancer. FIT is the preferred option of the USMSTF.

A limitation of the g-FOBT is it can't distinguish blood from colorectal cancer or polyps from blood originating elsewhere in the colon or upper intestinal tract. FIT specifically identifies blood from the colon, but while it can detect colorectal cancer, it's less effective at identifying polyps, Dr. Church says.

A newer option is stool DNA testing (Cologuard[R]), which is performed at home and includes a FIT test and molecular testing for DNA changes that indicate colorectal cancer or polyps. Research suggests the test detects 92 percent of colorectal cancers (comparable to colonoscopy) and 69 percent of high-risk adenomas (better than FIT), Dr. Church says, but it has a higher false-positive rate than FIT. "If I have a patient whose colon is such that I can't scope them, I would advise them to get a Cologuard," Dr. Church says.

Ages & Intervals

The ACS recommendation to begin colorectal cancer screening at age 45 for people at average risk is in response to rising rates of the disease among people under age 50. Those in good health and who are expected to live more than 10 years should continue regular screening through age 75, the ACS notes. From there, people ages 76 to 85 should carefully weigh the risks and benefits of screening with their doctors, while those over age 85 should no longer be screened, the ACS advises.

However, your need for screening should be based more on your overall health and life expectancy, along with previous screening results, Dr. Church cautions. "If someone has had a negative colonoscopy at age 50, 60, and 70, odds are it's going to be negative after that," he adds. "But, if they've produced polyps at each of their screenings, they should continue to screen until their life expectancy is no more than five years."

Similarly, Dr. Church says your screening history should determine your screening intervals. For instance, he says, finding three or more adenomatous polyps, more advanced polyps, or a polyp with high-risk features, such as high-grade dysplasia, warrants a repeat colonoscopy within three years.

"We're not saying to a patient that this is your interval for life. We're saying this is your interval right now, based on what's happening in your colon," he says. "Think of the colon as a garden, and polyps are weeds. Some gardens don't produce any weeds, and they're fine. Others produce weeds all the time, and you have to tend them all the time."


Guidelines from the American Cancer Society recommend these screening tests and intervals for people at average risk of colorectal cancer:

Visual exams

* Colonoscopy: every 10 years

* Flexible sigmoidoscopy: every 5 years

* CT colonography: every 5 years

Stool-based tests

* High-sensitivity (H-S) fecal immunochemical test: yearly

* Multi-targeted stool DNA test: every 3 years

* H-S guaiac-based fecal occult blood test: yearly

Note: People are considered to be at average risk if they do not have a personal history of colorectal cancer or certain types of polyps, a family history of colorectal cancer, a family history of precancerous colorectal polyps, a personal history of inflammatory bowel disease, a hereditary colorectal cancer syndrome (such as Lynch syndrome or familial adenomatous polyposis), or a personal history of radiation treatment to the abdomen or pelvis for a prior cancer.

Sources: American Cancer Society; James Church, MD, Cleveland Clinic

Caption: Colorectal cancer


Colonoscopy            Offers early detection/prevention of colorectal
                       cancer; affords visualization of entire colon
                       and removal of colorectal polyps

Flexible               Affords visualization of rectum, distal colon
sigmoidoscopy          and removal of polyps there; may not require
                       full bowel cleansing or sedation

CT colonography        Noninvasive; views entire colon; comparable to
                       colonoscopy for detecting cancer; no sedation

Capsule                Provides view of entire colon and digestive
colonoscopy            tract; no sedation needed

Multi-targeted         Detects cancer/polyps; no bowel prep, sedation;
stool DNA test         home-based; no diet/medication restrictions

Fecal immunochemical   Detects cancer/polyps; no bowel prep, sedation;
test(FIT)              home-based; no diet/medication restrictions;
                       many brands require only one sample

High-sensitivity       Safe; no bowel prep, sedation; home-based;
guaiac-based fecal     inexpensive; good evidence it reduces mortality
occult blood test


Colonoscopy            Effectiveness based on bowel prep quality,
                       skill of practitioner; full bowel prep &
                       sedation necessary; small risk of bowel

Flexible               Effectiveness determined by quality of bowel
sigmoidoscopy          prep, skill of operator; pain and discomfort;
                       requires enema beforehand

CT colonography        Full bowel prep; potential for false-positives;
                       expensive and may not be covered by insurance

Capsule                May not be covered by insurance; only for
colonoscopy            patients who can't complete optical colonoscopy

Multi-targeted         Higher false-positive rate than FIT; pricier
stool DNA test         than other stool tests; limited long-term data
                       on screening outcomes

Fecal immunochemical   Less effective at detecting advanced adenomas;
test(FIT)              high nonadherence to annual testing

High-sensitivity       Less effective at finding advanced adenomas;
guaiac-based fecal     high nonadherence to annual testing; diet/
occult blood test      medication restrictions necessary; requires
                       multiple samples; higher false-positive rate
                       than FIT

Note: A potential drawback for all tests except colonoscopy is that
any abnormal findings must be followed up with a timely colonoscopy.
Sources: American Cancer Society; James Church, MD, Cleveland Clinic
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Title Annotation:Cancer
Publication:Men's Health Advisor
Date:Nov 1, 2018
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