COLORECTAL CANCER SCREENING: Enough With the Excuses!

Jeff Fox, MD

As a gastroenterologist, probably the single biggest question I get asked is, “Do I have to get a colonoscopy?” In fact, many of my colleagues and friends confess that when they pass me on the street, they think of the colonoscopy they had, were supposed to have, or never got around to having. To them, I am like Katie Couric, “the face of colon cancer screening.” Embarrassed, am I? Absolutely not! There are few diseases where modern medicine has been more successful than in preventing colorectal cancer.

Efforts to prevent colorectal cancer (CRC) include many well-documented successes. In just the last 25 years, the incidence of CRC in the United States has been reduced by 33%, and death from CRC has dropped by 40%. Over half the mortality reduction is thought to be attributable to screening. Additionally, overall 5-year survival from CRC during the last 25 years has increased from 50% to 66%, largely due to early detection and improved treatments. Finally, more and more people are getting screened every year. At Northern California Kaiser Permanente, for example, nearly 80% of patients in the target 50-75 age range will have recorded up-to-date CRC screening in 2011, an all-time high. To approach this high level of adherence for CRC screening was once unheard of. Physicians should be very proud of these efforts.

Though some observers have attributed the declines in CRC incidence to an increase in colonoscopy screening, the procedure has only been used widely for screening during the last 10 years. The rise in colonoscopy screening occurred precisely when Medicare began reimbursing for colonoscopies for patients with average CRC risk. Yet, CRC mortality had been steadily declining well before that policy change. Physicians have been screening for colorectal cancer for more than 20 years, though earlier efforts were mostly by occult blood testing and flexible sigmoidoscopy, with colonoscopy reserved for positive tests only. In other words, the successes in CRC screening aren’t just attributable to colonoscopies. Instead, they are successes of population-based screening with all available modalities.

So which modality should be used in which patient? I believe that every patient who is reasonably healthy and is in the appropriate screening age range (50-75 years, older than which the overall risk of screening outweighs the benefits) with at least a 5-year life expectancy should be offered CRC screening. In 2008, both the U.S. Preventive Services Task Force (USPSTF) and a multispecialty task force comprised of gastroenterologists, radiologists and oncologists (MTF) published lists of recommendations for colorectal cancer screening. Three screening modalities made both lists as “recommended” tests: high-sensitivity fecal occult blood testing annually, flexible sigmoidoscopy every five years, and colonoscopy every 10 years. The other available tests (CT colonography, double-contrast barium enema and fecal DNA testing) were not supported by both task forces.

The pros and cons of all six tests are reviewed below.

Occult blood testing

PROS: Evidence-based means of reducing colorectal cancer incidence and mortality (i.e. randomized, controlled trials proving effectiveness). Convenient, inexpensive, well-tolerated by patients, zero risk. Immunochemical testing (FIT) improves sensitivity for colorectal cancer to 60-90%. FIT is the form of occult blood testing used in most settings now, including at Kaiser Permanente, and the only kind that was recommended by both USPSTF and MTF.

CONS: High false positive rate. Requires serial testing to show benefits.

Flexible sigmoidoscopy

PROS: Evidence-based means of reducing colorectal cancer incidence and mortality. Able to detect polyps/cancer in the distal (left) colon and biopsy/remove at the same time. Convenience, cost and risk to patient are intermediate, relative to other modalities.

CONS: Patient discomfort when unsedated; sensitivity poor for proximal (right) colon disease as a stand-alone test.

Colonoscopy

PROS: High sensitivity and specificity for polyps and cancer. Able to detect polyps/cancer in both proximal and distal colon and biopsy/remove at same time. Patient must be sedated.

CONS: Safety—has 10 times the perforation risk of a sigmoidoscopy (1/1000 vs. 1/10,000). Costly. Inconvenient. Use of colonoscopy is supported only by surrogate outcomes, not by randomized trials.

Colonoscopy is used to investigate positives from other modalities, but it appears to be limited in screening the proximal colon. Efforts to sharpen optics, prolong the examination time and improve bowel preparation could increase the sensitivity of colonoscopy in the proximal colon.

Other tests

CT colonography (virtual colonoscopy). Similarly high sensitivity as colonoscopy for polyps and cancer. Concerns about radiation exposure risk (i.e., iatrogenic malignancies) and missed “flat polyps” make CT colonography a less than ideal screening tool (and not reimbursed by many insurance companies). However, CT colonography is a good alternative to colonoscopy as a reasonably accurate test when colonoscopy is not feasible.

Double contrast barium enema. Poor sensitivity and radiation exposure make this a less favored choice for screening when other modalities are available.

Fecal DNA testing. Initial promise was thwarted by relative costliness and nearly identical sensitivity to the much less expensive fecal immunochemical testing. Still primarily investigational.

The current buffet of screening options exists because there is no “perfect” screening test for CRC. The ideal test would be something as simple, tolerable and inexpensive as the occult blood test with the accuracy of colonoscopy (or better). This perfect test unfortunately does not appear to be on the near horizon, so I expect we will be making do with what we have for at least the next few years.

Nevertheless, with the buffet approach, we are continuing to improve screening rates nationally. And it’s working—colorectal cancer incidence and mortality continue to decline. The important message that I advise physicians to give to patients is: Get screened. Don’t get too bogged down on the details, and certainly don’t let indecision or excuses prevent you from getting screened.

Here are the most frequent excuses I hear, along with sample responses:

EXCUSE: “I’m too busy to have a colonoscopy/sigmoidoscopy.”

RESPONSE: “FIT takes five minutes and can be performed in the comfort of your own home.”

EXCUSE: “Won’t FIT or sigmoidoscopy miss something?”

RESPONSE: “No test is perfect, including colonoscopy. Despite those limitations, both occult blood testing and sigmoidoscopy are proven to reduce your risk of colorectal cancer and death. If you are willing to acknowledge the additional risk and inconvenience of a colonoscopy, it is an acceptable method of screening.”

EXCUSE: “I don’t want to know.”

RESPONSE: “Colon cancer is preventable without surgery or chemotherapy when caught early or in the pre-cancerous stage. You can’t find it in those stages unless you get screened.”

EXCUSE: “I don’t have any symptoms, so why bother?”

RESPONSE: “Colon cancer and pre-cancerous polyps are usually asymptomatic until it’s too late.”

EXCUSE: “The prep sounds horrible.”

RESPONSE: “FIT requires no prep. And there are lower-volume sigmoidoscopy and colonoscopy preps available through many providers.”

So tell your patients what I tell them: “Enough with the excuses! Get screened. Period.” I don’t mind being the face of colorectal cancer screening because I could save your life.

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Dr. Fox is a gastroenterologist at Kaiser San Rafael.

Email: jeff.fox@kp.org