Screening colonoscopy: Quality, public awareness key to efficacy

Emphasizing quality indicators and promoting public awareness will improve patient outcomes and increase screening rates in the future.

Each year, about 14 million screening colonoscopy procedures are performed, ranking colonoscopy as one of the most widely used endoscopic procedures in the United States.

However, the efficacy of the procedure rests heavily on its quality, an issue that is emerging as a major concern in the gastroenterology and endoscopy communities, according to Douglas Rex, MD, FACP, FACG, professor in the department of medicine, division of gastroenterology and hepatology, Indiana University School of Medicine, and director of endoscopy at Indiana University Hospital.

Recent data have questioned the accuracy and effectiveness of colonoscopy as commonly performed in the medical community and demonstrated the importance of quality indicators.“There is a lot of room for improvement in terms of the quality of colonoscopy, and those steps are now being taken,” said David A. Lieberman, MD, FACG, professor of medicine, head of the division of gastroenterology at Oregon Health and Science University and Portland Veterans Affairs Medical Center, and member of the Oregon Health & Science University Knight Cancer Institute.

“First, we need to identify the things that should be monitored as part of high-quality practice and once we recognize that the performance is not what we’d like it to be, we need to improve it.”

Experts like Rex and Lieberman have played instrumental roles in providing recommendations and guidelines to ensure high-quality performance, either in private practices or large institutions. According to Rex, the efficacy of the procedure is probably not 90%, as was once reported.

Questioning the efficacy

In 1993, the National Polyp Study provided evidence for the long-held belief that colon cancer arises from adenomas and that removal of adenomas would interrupt that pathway. Data from the National Polyp Study, led by Sidney Winawer, MD, MACG, Paul Sherlock Chair in Medicine, and attending physicians on the GI and nutrition service at Memorial Sloan-Kettering Cancer Center, demonstrated that colonoscopy was associated with a significant decrease in colon cancer incidence, ranging from 76% to 90%.

The study included 1,418 patients who had one or more adenomas removed during colonoscopy. Patients then underwent periodic colonoscopy during an average follow-up of 5.9 years. The researchers compared the colon cancer incidence rates with those from three reference groups: two cohorts where polyps were not removed and one general-population cohort.

Douglas Rex, MD, FACP, FACG, has played an instrumental role in providing recommendations to ensure high-quality colonoscopy. Photo by Lora Lisa Willkie

Almost all patients (97%) were followed for 8,401 person-years. Colonoscopy detected five malignant polyps all with early stage curable asymptomatic cancers. Based on the rates in the reference groups, the numbers of colorectal cancers expected were 48.3, 43.4 and 20.7, respectively, for reductions in the incidence of colorectal cancer of 90%, 88% and 76% in patients who had polyps.

Based on these and other case-controlled data, the U.S. Multi-Society Task Force included screening colonoscopy in its guidelines for the first time in 1997. Although the NPS data refer to patients who have had polyps removed, the precise benefit of screening colonoscopy in the general population has not been determined. A study published in Annals of Internal Medicine demonstrated a 67% overall reduction in mortality from colorectal cancer from screening colonoscopy. There was a 1% reduction in mortality from cancers on the right-side of the colon. Based on these results, researchers feel that patients should be informed that colonoscopy reduces the risk for getting colorectal cancer but the precise percentage is not known.

“Like most retrospective studies, this is more hypothesis-generating and kind of focuses on where we need to go for future research, rather than being definitive information,” Douglas O. Faigel, MD, professor of medicine, division of gastroenterology at Oregon Health & Science University, and member of the Oregon Health & Science University Knight Cancer Institute, told HemOnc Today.

The study included 10,292 case patients and 51,460 controls identified from administrative claims data; 719 cases and 5,031 controls had had a colonoscopy. According to the researchers, complete colonoscopy was associated with fewer deaths from left-sided colorectal cancer (OR=0.33; 95% CI, 0.28-0.39) compared with right-sided colorectal cancer (OR=0.99; 95% CI, 0.86-1.14).

The explanations for this finding are unknown, though some have hypothesized a possible biological difference between the right and left colons. In addition, the study had other limitations, including a lack of data regarding the completeness of the exams, the use of claims data, and particularly relevant, the unknown quality of the exams. Most colonoscopies (70%) were performed by non-gastroenterologists.

Operator-dependent quality measures

Many quality indicators outlined in recommendations and guidelines include operator-dependent measures like skill, withdrawal time and adenoma detection rate. Using such guidelines as tools in practice will improve outcomes and ultimately lower colorectal cancer incidence rates.

“The quality of the procedure is emerging as a big deal and may account, more than any other cause, as the reason for why patients develop interval cancers,” Rex said.

This quality evidence is based partly on data from a study published in The New England Journal of Medicine that examined the quality of 7,882 colonoscopies performed during a 15-month period by 12 experienced gastroenterologists. Neoplastic lesion detection rates were compared among gastroenterologists — those with a mean withdrawal time < 6 minutes and those with a mean withdrawal time ≥ 6 minutes.

Compared with colonoscopists with withdrawal times < 6 minutes, those with withdrawal times ≥ 6 minutes had higher rates of detection of any neoplasia (11.8% vs. 28.3%) and advanced neoplasia (2.6% vs. 6.4%).

Withdrawal time appears to be closely associated with adenoma detection rates. According to the U.S. Multi-Society Task Force, adenomas should be detected in ≥ 25% of men and ≥ 15% of women aged 50 years and older. This detection rate should help reduce the risk for incident cancers occurring after clearing colonoscopy and is fundamental to the execution of near complete protection against incident colorectal cancers, according to the American Society for Gastrointestinal Endoscopy Taskforce on Quality Assurance in Endoscopy.

David A. Lieberman

According to Faigel, once a colonoscopist with a low adenoma detection rate is identified, it is easiest to raise that rate by working to improve the withdrawal time. Winawer agrees, noting that recent studies have indicated that time to withdrawal is not necessarily the key, but that colonoscopists with slower withdrawal times are more likely to perform more meticulous exams.

The guidelines also state that cecal intubation is needed because of the substantial number of colorectal neoplasms located in the proximal colon and cecum. According to Rex and his colleagues at the ASGE Taskforce on Quality Assurance in Endoscopy, colonoscopists should document cecal landmarks as they identify them.

“Colonoscopists need to document by photography and notation of landmarks that they have actually reached the beginning of the colon. That means getting the scope tip all the way into the cecum so that the area between the ileo-cecal valve and the opening to the appendix can be well visualized,” Rex said.

Operator-dependent factors such as withdrawal time, adenoma detection rate and cecal intubation rate are imperative to the success of screening colonoscopy, as is patient compliance with bowel preparation.

Patient factors affect quality, screening rates

“The biggest place where we need a better mousetrap is preparation,” Faigel said. “The preparation is pretty unpleasant and it doesn’t always work well; we don’t always get as clean a colon as we’d like, which is probably a big reason for missing a lesion.”

According to some experts, patients need to understand the association between bowel preparation and high-quality colonoscopy. Apart from choosing a gastroenterologist to perform the procedure, bowel preparation is one area where patients can help ensure the quality of their exam.

Recently, data have demonstrated the superiority of a split-dosing regimen for bowel preparation, opposed to a single dose of a laxative. Split dosing involves giving half of the bowel preparation the day before the exam and the second half on the day of the exam. According to Rex, this method helps clean out mucus and intestinal secretions that collect overnight and impair the detection of flat and depressed lesions in the cecum.

Many adults, however, are unwilling to undergo the procedure. Between 1987 and 2005, screening colonoscopy rates among patients aged 50 and older rose from about 32% to 50%. Many patients view the procedure as embarrassing, inconvenient, unpleasant and uncomfortable.

The use of CT colonography may increase screening rates, especially among those unwilling to undergo traditional colonoscopy.

“The American public is under-screened; we need a screening tool that’s more appealing and better tolerated by patients,” Judy Yee, MD, chief of radiology at the San Francisco Veterans Affairs Medical Center and vice-chair of the department of radiology, told HemOnc Today. According to Yee, CT colonography is the perfect candidate due to its less invasive nature and the lack of sedation associated with the procedure.

But its use is controversial. Though data have demonstrated the ability of CT colonography to detect adenomatous polyps, many patients who undergo the less invasive exam may require colonoscopy to remove the polyps. In such cases, patients would need a second bowel preparation and would need to undergo an additional examination for polyp removal. One way to bypass the second preparation is to perform the colonoscopy immediately after polyps are detected on the CT colonography. According to Yee, this situation would be ideal.

Although screening CT colonography may be a viable option for fearful patients, the use of the procedure in the general population has raised some red flags due to radiation exposure. According to Yee, new CT scanners limit radiation to doses similar to those associated with other screening tools like contrast barium enema.

Though CT colonography cannot replace colonoscopy because it cannot include biopsies or polypectomy, the procedure is now validated by the American Cancer Society as a screening tool for colorectal cancer. Following the recent decision by the Centers for Medicare and Medicaid Services to not reimburse screening CT colonography the American College of Radiologists and other societies are working to find an alternate means of reimbursement.

Improving colonoscopy

Researchers in Europe are currently conducting a randomized controlled trial to determine the efficacy of screening colonoscopy on colorectal cancer incidence and mortality. The Northern-European Initiative on Colorectal Cancer (NordICC) trial will randomly draw 66,000 patients from population registries to compare screening colonoscopy with a control group of non-screened individuals after 15 years of follow-up.

“This trial is going to give us a lot of information that we need,” Winawer said. He and others tried to launch a similar study nearly 15 years ago, but the National Cancer Institute was not interested. According to Winawer, however, the NordICC trial is timelier due to the number of questions that have been raised about the value of screening colonoscopy.

In addition to randomized clinical trials, physicians are continuing to push for higher quality colonoscopies and increased public awareness. Currently, organizations like the ASGE, the U.S. Multi-Society Task Force and the National Colorectal Round Table are behind the quality assurance movement in colon cancer prevention.

“This is just the beginning of quality assurance in this field,” Winawer said. “We became cognizant of this just within the last few years, and we have to understand that screening colonoscopy is relatively new.”

In addition to guidelines and recommendations, the ASGE is spearheading a national endoscopic database reporting system to track individual and group performance.

Public awareness is also a priority, not only to increase screening rates but to educate the public about the uniqueness of colon cancer screening. Patients should not only be aware of the high prevalence of colon cancer but also of the fact that it is highly preventable, Winawer said.

According to Faigel, improving insurance coverage for the uninsured, providing better access to care, and involving primary care physicians are all vital tools to increase screening rates.

“The easiest thing, of course, is education and making sure that primary care physicians specifically have this on their radar screens. Patients need to be screened for colon cancer,” Faigel said. “For example, ASGE has been reaching out to gynecologists because they serve as primary care physicians for many women.”

ASGE is currently asking gynecologists to be advocates for their patients to receive colonoscopies or other appropriate screening, he said.

“We need to keep hammering away and increasing awareness,” Winawer said. “Colon cancer really provides a unique opportunity, one that is very different than screening for any other cancer. Here we can find the premalignant polyps and remove them to prevent cancer altogether; you can’t do that for prostate, breast or lung cancer.” – Stacey L. Adams

Does CT colonography have a role in colorectal cancer screening?

For more information:

• Barclay RL. N Engl J Med. 2006;355:2533-2541.
• Baxter NN. Ann Intern Med. 2009;150:1-8.
• Cancer Trends Progress Report – 2007 Update. National Cancer Institute website. http://www.cancer.gov
• Colon Cancer Screening Rates on the Upswing. American Cancer Society website. http://www.cancer.org
• w D. N Engl J Med. 2006;355:2588-2589.
• Ransohoff DF. Ann Intern Med. 2009;150:1-3.
• Rex DK. Am J Gastroenterol. 2006;101:873-885.
• Seeff LC. Gastroenterology. 2004;127:1670-1671.
• Winawer SJ. Gastroenterology. 2003;124;544-560.
• Winawer SJ. N Engl J Med. 1993;329:1997-1981.