If patients looked at the evidence, it's likely that everyone would get a colonoscopy by age 50. Screening reduces mortality and colonoscopy specifically even prevents cancer by removing polyps before they progress from adenoma to carcinoma. But patients' discomfort with the idea of invasive tests has kept screening levels below 60%, and colorectal cancer remains the country's second-leading cause of cancer death.
“A mammogram is going to diagnose cancer at an early stage. But it doesn't really help you to prevent the onset of cancer,” said Cary P. Gross, ACP Member, associate professor of medicine at the Yale University School of Medicine. Conversely, with colon cancer, detection is prevention because pre-cancerous polyps can be removed before they become invasive malignancies. Even when polyps turn cancerous, five-year survival is 90% when cancer is localized to the bowel, 68% when involving lymph nodes and 10% when metastasized, based on a SEER Cancer Statistics Review from the National Cancer Institute.
A study in the Jan. 6 issue of Annals of Internal Medicine provides further evidence of the screening's effectiveness. The study examined more than 10,000 case patients and 51,000 matched controls and found colonoscopy is associated with fewer deaths from colorectal cancer, primarily from left-sided cancers.
However, proper screening is hindered by squeamishness by patients or even possibly by physicians. Often, says Jorge Prieto, MD, a gastroenterologist with Thomas Jefferson University in Philadelphia, patients may have a natural bias against doing an invasive test for which they have no symptoms (See sidebar, ““).
George Tzanis, MD, a general internist in primary care at the Wilmington, Del., VA, agrees. “Most people who are resistant to it think that it is incredibly invasive for a screening test, and I agree. But it's probably the best way to do it.”
Getting the word out is one way of overcoming patients' fears. Colon cancer screening rates rose after news anchor Katie Couric underwent a live, on-air colonoscopy on the Today Show in March 2000, following her husband's death from colon cancer two years before. Calling it the “Katie Couric effect,” an article in the July 14, 2003 Archives of Internal Medicine reported that screening by 400 participating endoscopists increased from 15.0 colonoscopies per physician per month before the campaign to 18.1 after the campaign (P<.001).
Since then, cancer groups and medical societies have tried to sustain the public awareness and screening rates have increased to as high as 60%, compared with rates of 24.2% for ages 50 and up in 1987 and 37.1% in 1998, according to the National Health Interview Survey from 2001. The pressure is again on primary care physicians to convince their patients that any discomfort or embarrassment is far outweighed by the benefits of getting screened.
“Internists are at the forefront of this,” Dr. Prieto said. “They are the ones whose patients rely on them to recommend tests. It's really very important for the primary care physician to provide the proper advice.”
Click here to watch Dr. Prieto discuss ways to encourage patients to undergo colonoscopy screening.
Which test to recommend?
Two major updates were released in 2008, one jointly by the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer and the American College of Radiology, in May and the other by the U.S. Preventive Services Task Force (USPSTF) published in the Nov. 4 issue of Annals.
Both guidelines recommending that screening should begin at age 50. But the two groups' recommendations differed on some points. USPSTF only makes a recommendation if there is sufficient evidence, while the joint guidelines incorporated expert opinion when evidence is lacking.
David A. Lieberman, MD, from the Division of Gastroenterology/Hepatology at Oregon Health and Science University, sat on the joint guidelines panel that decided colon cancer prevention should be the main goal of colorectal cancer screening.
“Where we lacked ideal evidence from clinical studies, we provided expert opinion, because we felt that the readership, which is primary care providers, still needed to have some guidance with regard to these tests,” Dr. Lieberman said.
For example, USPSTF guidelines say that the decision to screen should be based on individual circumstances and health between age 75 and 85 and end by age 85, whereas the joint guidelines do not set an upper age limit. (These recommendations apply to average-risk individuals who do not have a parent, sibling or child with colon cancer.)
Also, USPSTF guidelines do not divide the tests into categories or cite advantages to one over the other, noting that evidence is insufficient to recommend a specific screening method. But the joint guidelines divide tests into two major categories. The first category is tests that primarily detect cancer, fecal occult blood testing (FOBT) or DNA stool tests, that need to be done annually. The second is structural screening tests, which view the colon directly and can detect polyps. Options include flexible sigmoidoscopy, CT colonography or double-contrast barium enemas, which should be done every five years, or colonoscopy, which also allows for polyp removal and should be done every 10 years.
Theory vs. practice
Despite a lack of randomized, controlled trials, gastroenterologists prefer colonoscopy as the gold standard because it allows complete visualization of the entire colon. Any polyps found can be removed for biopsy and average risk individuals with a normal colonoscopy need not be rescreened for 10 years, said Dr. Prieto.
However, flexible sigmoidoscopy is a reasonable and recommended procedure, considering that the evidence is lacking on whether colonoscopy is beneficial for average-risk individuals, according to ACP's point-of-care guidelines, PIER, which recommend annual FOBT and then flexible sigmoidoscopy. There are fewer complications, the bowel prep is easier, and it can be done by general internists and nurse practitioners, said Dr. Gross, editorial consultant for PIER's colon screening module.
However, at the Yale clinic he oversees, Dr. Gross said he implements colonoscopy as the preferred screen. “There is great circumstantial evidence that suggests that colonoscopy is better and that's why I recommend it for my patients. But there's not incredibly strong evidence as of yet that says we have to be choosing colonoscopy as our first choice. There is just no prospective randomized trial to compare colonoscopy to other modalities.”
Hemant Roy, MD, an associate professor at Northwestern University's Feinberg School of Medicine and of the department of internal medicine at Evanston (Ill.) Northwestern Healthcare, agreed that in his practice, colonoscopy is the gold standard. But he understands that it's not always available in every region. “From a societal point of view, if you think about delivery of health care, access to health care, cost and other availability, one could make an argument that flexible sigmoidoscopy is a reasonable option to offer.”
There are advances in stool tests, too. FOBTs are widely available, and newer tests not yet on the market that screen for DNA of precancerous adenomas “could provide a valuable noninvasive option that is superior to conventional occult blood testing,” said an editorial in the Oct. 7 Annals.
But, said Dr. Gross, stool tests need to be repeated annually, and must be followed by a colonoscopy if there's an abnormal result. “If some people are telling you they really don't want to get a colonoscopy—it's something they're strongly against—don't tell them ‘OK, we have a great alternative, it's called a stool test.’”
Yet, the evidence reviewed by the USPSTF suggests that annual high sensitivity occult blood screening followed by colonoscopy for those who test positive will save close to as many lives as primary colonoscopy screening. Many physicians at the primary care level prefer to provide patients options to enhance compliance with screening, said Michael LeFevre, MD, in family practice at the University of Missouri and a member of the USPSTF panel that updated colon screening guidelines.
“I can see a practicing physician doing that precise thing,” said Dr. LeFevre. “It's difficult, quite frankly, to implement a program of screening where someone has to check for occult blood every year. In small offices, [doctors] may just say, I'd rather people do colonoscopy, but if they don't I'll offer them this. The evidence is good that it saves lives.”
Dr. Gross added. “You should really only do the stool test if you are understanding and planning that you'll follow up the abnormal tests with an appropriate colonoscopy workup.”
In all cases, informed consent should spell out the details of which test, why and when.
“Patients do need to be informed about what the goal of the test is,” Dr. Lieberman said. “If the primary goal of the test is early cancer detection, they need to be told that. And if the primary goal of the test is both early detection plus prevention, they need to be told that.”