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New research identifies more effective tools for detection of colorectal cancer

02.06.2009
Health outcomes explored at DDW 2009

The latest advances in polyp detection, assessment of colorectal cancer risk, and patient sedation during colonoscopy will be presented today at Digestive Disease Week® 2009 (DDW®).

Research regarding the size and type of polyps detected during colonoscopy and the risk associated with developing colon cancer offers new insight into the recommended frequency of follow-up preventive colonoscopy. New research also examines the risk of perforation during colonoscopy and new tools allowing physicians to more closely examine polyps during colonoscopy including optical biopsy and deep sedation of the patient will be presented.

DDW is the largest international gathering of physicians and researchers in the fields of gastroenterology, hepatology, endoscopy and gastrointestinal surgery.

"Advances in technology and our ability to assess polyps during colonoscopy are the key to early detection of colorectal cancer. Perfecting the frequency of colonoscopy and identification of potentially cancerous polyps are the latest in our arsenal in the fight against this cancer," said Kenneth K. Wang, MD, AGAF, FASGE, Mayo Clinic, Rochester.

More Large Polyps Are Seen on Screening Colonoscopy with Deep Sedation Compared with Moderate Conscious Sedation (Abstract #722)

Deep sedation (DS) during colonoscopy may result in greater detection of polyps, which could save more lives by alerting doctors and patients to colon cancer at its earliest, most treatable stages.

Investigators sought to discover whether patients who are more fully sedated during colonoscopy are more likely to have polyps detected because the patient is more relaxed and the physician can focus completely on polyp detection. Patients who are deeply sedated are not awake, whereas patients under moderate conscious sedation (MCS) are able to hear and respond to directions during the procedure.

Researchers examined a database detailing endoscopy reports from 61 practice sites across the U.S. from patients who underwent average risk screening colonoscopy done with MCS or DS. They found that even with no difference in prep quality between the two sedation levels, significantly more large polyps were found with DS than with MCS, even after controlling for such factors as age, gender and race; the rate of polyps detected was 25 percent more in patients sedated using deep sedation.

"We don't know for sure whether these polyps would have been found if the patients were examined under moderate sedation," said Katherine M. Hoda, MD, senior fellow, department of gastroenterology, Oregon Health & Science University. "Our study suggests that DS finds more polyps, which could have an impact on the way physicians conduct colonoscopies."

Dr. Hoda cautioned that further studies of many more patients are needed to compare the effects of DS and MCS. This study was small and not randomized, and because it entailed studying information in a database, it may be less definitive than looking at a larger, randomized trial.

Dr. Hoda will present these data on Tuesday, June 2 at 10:30 a.m. CDT in S104, McCormick Place.

Large Tubular Adenomas, Villous Polyps, and Lesions with High Grade Dysplasia: Can We Really Be Comfortable Waiting 3 Years Before Repeat Colonoscopy? A Retrospective VA Medical Center Study (Abstract #435)

After patients undergo colonoscopy with removal of advanced pre-malignant polyps, including those greater than 10mm in size and those with villous or high grade dysplastic features, current guidelines recommend that follow-up colonoscopy be performed after a 3 year interval. However, a recent study suggests that maybe this recommendation should be revisited, as patients who underwent colonoscopy sooner were found to have a high detection rate of advanced polyps, which are more likely to transform into colon cancer.

Investigators sought to examine a group of patients that are at higher risk for developing cancer and therefore require more frequent colonoscopy. The visualization and removal of large, villous, or high grade dysplastic polyps signifies the need for repeat colonoscopy in 3 years. All three of these features are typically considered equivalent, and it has been difficult to determine whether one of these polyp characteristics is more predictive of subsequent cancer.

"We wanted to evaluate whether or not one of these polyp features is more predictive of subsequent cancer, and whether 3 years is always appropriate," said Jonathan Mellen, MD, gastroenterology fellow, Phoenix VA Health Care System. "In addition, we wanted to find out more about how a sooner second colonoscopy or a subsequent third colonoscopy might maximize the level of cancer prevention."

Investigators reviewed data from more than 25,000 colonoscopies and only included patients with advanced polyps removed and who underwent both a second and third colonoscopy. Patients were divided into three groups according to which advanced polyp feature was reported. They found that all three groups had a substantial rate of advanced polyp detection at second colonoscopy. The study found that removal of polyps with villous and high grade features was particularly predictive of more future advanced polyps and therefore increased susceptibility to cancer.

In addition, they found that the rate of discovering advanced polyps at third colonoscopy was less than second colonoscopy, although still high enough to suggest that continued exams in this group is an efficient use of resources.

Dr. Mellen will present these data on Monday, June 1 at 3:15 p.m. CDT in S104, McCormick Place.

Can We Really Expect a Therapeutic Benefit After Two Preventive Colonoscopies? A Retrospective VA Medical Center Study (Abstract #432)

A new report suggests that although patients are recommended to undergo multiple repeat colonoscopies after removal of pre-malignant polyps, some of these patients might have a risk of colon cancer that is no greater than the general population after two colonoscopies. This study found that patients with consecutive colonoscopies performed at least three years apart, with at least one being free of tubular adenomas (the most common type of premalignant polyp), are at very low risk of developing colon cancer after a second colonoscopy.

Current guidelines usually call for repeat colonoscopy anywhere from three to five years after removal of premalignant polyps, based on the number, size and microscopic description of the polyps removed. Depending on results of the second colonoscopy, a third is recommended after another three to five years despite a small body of evidence supporting this practice.

"This is problematic because as more of our resources are dedicated to these repeat colonoscopies, more resources are diverted away from our goal of screening the entire population over 50," said Jonathan Mellen, MD, gastroenterology fellow, Phoenix VA Health Care System. "These findings could help reduce the number of unnecessary colonoscopies, and therefore facilitate more opportunity to perform screening exams. The overall goal is to create a more efficient way to prevent colorectal cancer with reasonable use of our resources."

Investigators sought to determine the value of performing a third colonoscopy on a patient who had already undergone two previous exams. They reviewed endoscopic data from more than 25,000 colonoscopy reports; patients were included if they had undergone at least three colonoscopies, with a three year interval between exams. A total of 154 patients were included, and these patients were grouped according to whether they had pre-malignant polyps removed during the first two colonoscopies.

Results found that patients who had pre-malignant adenomas removed during both the first and second colonoscopy were at higher risk for developing subsequent pre-malignant adenomas after the second colonoscopy. Most importantly, more than 8 percent of this group had more concerning, advanced adenomas removed at the third colonoscopy (including one cancer) vs. 0 percent for all other patients. Although patients with a negative first or second colonoscopy might be appropriate for a third examination after a 10 year interval (similar to the general population), the group with adenomas found at first and second colonoscopy should undergo third colonoscopy as dictated by current guidelines, Mellen said.

Dr. Mellen will present these data on Monday, June 1 at 2:15 p.m. CDT in S104, McCormick Place.

Optical Biopsy at Colonoscopy: Are We Ready? DISCARD Study: Early Results (Abstract #721)

Researchers have studied a method that may be more effective at examining and identifying polyps that are precancerous, thereby eliminating the time and expense of sending biopsies to pathology.

Under the current colonoscopy protocol, the majority (90 percent) of polyps removed during the procedure are small, less than 10mm, in size and are sent for evaluation of pathology after removal. The removal of polyps reduces the risk of cancer and the number of polyps removed is the basis for determining the frequency of subsequent colonoscopies. Typically, only half of the polyps removed during colonoscopy are discovered to be precancerous.

In a study at St. Mark's Hospital in London, investigators followed four endoscopists with varying levels of experience with optical diagnosis during colonoscopies. The participating colonoscopists used one or a combination of optical modalities to predict the histopathology of each polyp encountered. Each polyp was then removed and sent for formal histopathology. Researchers found that out of the 85 adenomas removed, 92 percent were correctly diagnosed and of the 38 hyperplastic polyps, 95 percent were correctly diagnosed by the colonoscopists making the optical diagnosis.

"Optical diagnosis allows us to predict accurately whether a polyp should be removed immediately during the colonoscopy. This not only spares the patient the risk involved in the unnecessary removal of non-precancerous polyps, but eliminates the wait time and expense involved in the current protocol of sending biopsies to pathology," said Ana Ignjatovic, BMBCh, endoscopy research fellow at the Wolfson Unit for Endoscopy at St. Mark's Hospital.

Both Dr. Ignjatovic and Brian P. Saunders, MD, director of the Wolfson Unit for Endoscopy, believe that the next steps should be to expand the study beyond an academic center to determine the level of training that would need to be provided before the procedure could be used on a wider scale.

Dr. Ignjatovic will present these data on Tuesday, June 2 at 10:30 a.m. CDT in S406A, McCormick Place.

Risk of Perforation During Colonoscopy: A Systematic Review and Meta-analysis (Abstract #210)

Perforation rates for both diagnostic and therapeutic colonoscopies are quite low and reported rates are decreasing, according to the largest analysis to date of colonoscopy perforation rates.

Using meta-analysis, a type of systematic review that includes formal statistical techniques to combine the results of previous research, investigators under the mentorship of Philip S. Schoenfeld, MD, at the University of Michigan sought to establish an accurate measure of colonoscopy perforation rates. According to previous research, reported rates of perforation in the literature range from as low as 0.01 percent (1 in 10,000) to as high as 1.1 percent (1 in 100).

"Perforation is one of several potential complications of colonoscopy including cardiopulmonary events, hemorrhage and pain," said S. M. Abbas Fehmi, MD, MSc, clinical faculty at University of Pennsylvania School of Medicine. "Of these risks, perforation has been considered by some to be the most serious, so we wanted to determine the actual rate of perforation to help patients and their physicians make informed decisions. The good news is that we found the risk of perforation during colonoscopy is extremely low."

Fehmi and his colleagues searched databases from 1950 through 2007 for all English language abstracts of prospective studies related to perforation rates. They also reviewed abstracts presented at all major national and international gastroenterology meetings from 2005 to 2007. Seventeen studies, consisting of 274,265 colonoscopies, met the inclusion criteria.

Pooled perforation rate in therapeutic colonoscopies was found to be 0.066 percent or approximately 1 in 1500 and in diagnostic colonoscopies was found to be .017 percent or approximately 1 in 6000. Therapeutic colonoscopy, which is required to remove lesions if polyps are present, was associated with a higher risk of perforation. The analysis also identified a trend towards decreasing perforation rates for both therapeutic procedures and diagnostic procedures.

Fehmi said that while colonoscopy is a safe procedure, there are some risks that need to be explored further. Studies should be done in the community and university setting and patients should be stratified by different risk factors and indications. Future prospective studies should also employ a systematic follow up (at day seven or 30) to ensure capture of all complications. These quoted rates of perforation can serve as a quality, performance, or outcome benchmark.

Dr. Choksi will present these data on Sunday, May 31, 2009 at 2:15 p.m. CDT in S406A, McCormick Place.

DDW is the largest international gathering of physicians, researchers and academics in the fields of gastroenterology, hepatology, endoscopy and gastrointestinal surgery. Jointly sponsored by the American Association for the Study of Liver Diseases, the AGA Institute, the American Society for Gastrointestinal Endoscopy and the Society for Surgery of the Alimentary Tract, DDW takes place May 30 - June 4, 2009, at the McCormick Place Convention Center. The meeting showcases approximately 5,000 abstracts and hundreds of lectures on the latest advances in GI research, medicine and technology.

Aimee Frank | EurekAlert!
Further information:
http://www.gastro.org
http://www.ddw.org

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