Gastrointestinal Endoscopy June Issue Study Highlights

Main Category: GastroIntestinal / Gastroenterology
Also Included In: Cancer / Oncology
Article Date: 01 Jul 2009 - 0:00 PDT

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Polyp detection rates at screening colonoscopy; EUS-based criteria for the diagnosis of chronic pancreatitis

In the June issue of GIE: Gastrointestinal Endoscopy, the monthly peer-reviewed scientific journal of the American Society for Gastrointestinal Endoscopy (ASGE), a study looking at polyp detection rates at screening colonoscopy found a wide variation among endoscopists, though researchers note that further study is needed to determine the reasons for the variation and their clinical significance. Also in the June issue, researchers present a new criteria for the endoscopic ultrasound (EUS) diagnosis of chronic pancreatitis. A current lack in standardization in EUS terminology, features and criteria for the condition has made it difficult to reproduce study findings and apply them in clinical practice. The researchers believe the new criteria represent an improvement over the current means of EUS diagnosis, which assigns equal importance to each criterion.

"Variation in polyp detection rates at screening colonoscopy"

Colonoscopy is recommended as a primary screening method for colorectal cancer and is the final common pathway for all other recommended screening tests. It is considered the "gold standard" for colorectal cancer screening for its ability to diagnose and remove polyps (growths) before they turn into cancer. Colonoscopy uses a colonoscope, a tube with a light and video camera on the end, which allows the physician to see the entire colon. If a polyp is found, it can be removed immediately. The polyp is usually removed with small biopsy forceps or loop of wire (snare) that is advanced within a channel in the colonoscope.

Studies of screening colonoscopy have documented variation in adenoma (benign growth) detection rates between 10 percent and 50 percent. The clinical and medicolegal effects of missed lesions and the wide variation in polyp detection have created the need for quality standards for colonoscopy performance. The U.S. Multi-Society Task Force on Colorectal Cancer has established targets for continuous quality improvement. One such target is adenoma detection rates of 25 percent or greater for men and 15 percent or greater for women aged 50 years and older undergoing first-time screening colonoscopy. Another quality target is a mean minimum withdrawal time, currently suggested to be at least six minutes. With these targets in mind, researchers examined data from one of the longest ongoing programs of screening colonoscopy with the objectives of measuring the variation in polyp detection rates (PDRs) among endoscopists and identifying factors that account for the variation.

Researchers performed a retrospective cross-sectional analysis of summary-level data from endoscopists performing screening colonoscopy for the Lilly Colorectal Cancer Prevention Program in Indiana. All procedures were performed on average-risk, asymptomatic adults aged 50 years or older, who underwent first-time screening colonoscopy between September 1995 and June 2001. The study was approved by the institutional review board of Indiana University. The study included twenty-five endoscopists and 2,664 patients (1,108 women and 1,556 men). Summary-level data was analyzed for each endoscopist, including patient mean age, sex profile, mean procedure time, number of colonoscopies performed and the proportions of patients with any-sized polyp, any-sized adenoma, an adenoma one cm or larger in maximum diameter, and multiple (more than one) adenomas. Multiple linear regression analysis (a technique for determining the linear relationship between one dependent variable and two or more independent variables) identified factors that accounted for the variation in PDRs.

The mean procedure time (MPT) was 17.1 minutes. Adenoma detection rates ranged from seven percent to 44 percent and from zero percent to 13 percent for large polyps, which was not statistically significant. For all polyp categories, only one to three high outlier endoscopists (ie, higher than mean PDRs) were identified. Models that included the number of procedures, mean age, percentage of women, and MPT accounted for 36 percent to 56 percent of the variation in PDRs. Only MPT was significantly associated with PDRs across all models. Researchers concluded that PDRs vary widely among endoscopists, although only a few outliers (ie, endoscopists who had higher polyp detection rates) were identified, variation in PDRs was associated only with MPT and that further research is needed to determine the clinical importance of and reasons for this variation.

The researchers acknowledged several limitations including the use of summary-level data, which is more limited than individual data, indirect calculation of MPT, and whether each endoscopist's patient cohort was at comparable risk for colorectal neoplasia was uncertain.

In an accompanying editorial, Harminder Singh, MD, MPH, departments of internal medicine and community health sciences, University of Manitoba, Canada, and Gurkirpal Singh, MD, division of gasteroenterology and hepatology, Stanford University School of Medicine, Cal., stated that "whether the optimal withdrawal time to allow complete visualization of colonic mucosa for an average endoscopist should be six or 10 minutes or another time interval still needs to be better defined. Optimal withdrawal is essential to ensure complete colonic examination. Spending six or 10 minutes during withdrawal is a small price to pay for improving outcomes after colonoscopy."

"EUS-based criteria for the diagnosis of chronic pancreatitis: the Rosemont classification"

Endoscopic ultrasound is increasingly used in the evaluation of chronic pancreatitis. Chronic pancreatitis is a continuing inflammatory disease of the pancreas characterized by irreversible morphologic changes often associated with pain and loss of exocrine or endocrine function.

Endoscopic ultrasound consists of a flexible endoscope which has a small ultrasound device built into the end. The ultrasound component produces sound waves that create visual images of the digestive tract which extend beyond the inner surface lining. EUS can be used to evaluate an abnormality below the surface such as a growth that was detected at a prior endoscopy or by X-ray. EUS can also be used to diagnose diseases of the pancreas, bile duct, and gallbladder when other tests are inconclusive, and can be used to determine the stage of cancers. Tissue samples, using a fine needle aspiration technique (FNA), can be obtained in real time with EUS guidance should an abnormality be seen. EUS is promising compared with other imaging modalities because it can potentially detect earlier forms of chronic pancreatitis.

Previous EUS-based classifications of chronic pancreatitis have used different EUS terminology, features, and criteria. Additionally, traditional radiographic criteria such as the Cambridge classification are dated. The authors' purpose was to establish consensus-based criteria for EUS features of chronic pancreatitis. An international consensus meeting was convened in Rosemont, Ill., in April 2007 attended by endosonographers from throughout North America and Japan who have expertise in evaluation and management of chronic pancreatitis. The conference was endorsed by the ASGE. Thirty-two internationally recognized endosonographers reviewed existing literature and discussed data before anonymously voting on terminology of EUS features, rank order, and category (major vs. minor criteria). Consensus was defined as greater than two thirds agreement among participants.

Major criteria for chronic pancreatitis were (1) hyperechoic foci with shadowing and main pancreatic duct (PD) calculi and (2) lobularity with honeycombing. Minor criteria for chronic pancreatitis were cysts, dilated ducts ≥3.5 mm, irregular pancreatic duct contour, dilated side branches ≥1 mm, hyperechoic duct wall, strands, nonshadowing hyperechoic foci, and lobularity with noncontiguous lobules. EUS findings were separated into major and minor criteria based on the stronger positive predictive value of major criteria which were thereby given more weight. The new Rosemont criteria, using a combination of major and/or minor criteria, categorizes the patient as having EUS features that are (1) consistent with chronic pancreatitis, (2) suggestive of chronic pancreatitis, (3) indeterminate of chronic pancreatitis, (4) normal.

The researchers concluded that the new Rosemont classification system represents an improvement over current means of EUS diagnosis for chronic pancreatitis. They acknowledge the results of their deliberations do not provide a validation of their recommendations, but intend to apply these criteria in a manner that provides easy and reproducible means of EUS diagnosis and grading of chronic pancreatitis so that they may be used to help guide patient care and future study design. In an accompanying editorial, Walter G. Park, MD, and ASGE President Jacques Van Dam, MD, PhD, FASGE, division of gastroenterology, Stanford University Medical Center, Cal., state that "despite being less than the perfect criterion standard, it remains the best to date."

Source:
Anne Brownsey
American Society for Gastrointestinal Endoscopy