Jan. 13, 2017
Patients with inflammatory bowel disease (IBD) are at increased risk of colorectal cancer (CRC), primarily due to chronic inflammation, which can cause the malignant transformation of normal epithelial cells in the gastrointestinal tract. The goal of CRC surveillance for these patients is the same as screening for the general population: To detect premalignant changes early enough to prevent cancer.
Unlike sporadic CRC, where the dysplastic lesion is usually a clearly visible colon polyp that can be resected at the time of colonoscopy, IBD-associated dysplasia often arises from flat, normal-appearing mucosa and historically has been difficult to detect. Thus, the traditional standard of care has required targeted biopsies of visible lesions and extensive random biopsies to identify invisible dysplasia. Yet this approach is not only time-consuming and costly, it is also inefficient — the random biopsy yield for dysplasia is 0 to 0.2 percent.
جزء مصبوغ من القولون أثناء التلوين التنظيري
يمكن أن يؤدي التلوين التنظيري إلى اكتشاف زيادة هائلة بآفات خلل التنسج في المرضى المصابين بأمراض الأمعاء الالتهابية (IBD).
In the last decade, the development of image-enhanced colonoscopy techniques and chromoendoscopy (CE) — the spray application of dye to the colonic mucosa — has improved neoplasia detection in IBD surveillance. By allowing identification of subtle structures in the mucosa, including flat lesions, CE has been shown to improve dysplasia detection rates fourfold in ulcerative colitis and Crohn's disease compared with random biopsy sampling. CE is also superior to other imaging modalities, including narrow band imaging, in differentiating between neoplastic and non-neoplastic changes and diagnosing the extent and inflammatory activity of disease.
In 2015, researchers at Mayo Clinic's campus in Jacksonville, Florida, reviewed key studies on the use of CE for colonic neoplasia detection in average and high-risk patients, including those with IBD. Their findings, published in Gastrointestinal Endoscopy Clinics of North America, showed that chromoendoscopy not only improves neoplasia detection but also has the potential to replace random biopsies as the optimal surveillance method.
In the same year, the American Society for Gastrointestinal Endoscopy (ASGE) and the American Gastroenterological Association (AGA) issued new recommendations for the surveillance and management of dysplasia in patients with IBD. Chief among them is the use of chromoendoscopy instead of white-light endoscopy (WLE) for both standard- and high-definition colonoscopy; surveillance instead of colectomy for patients with endoscopically resectable dysplastic lesions; and referral to an endoscopist with expertise in surveillance chromoendoscopy for patients with confirmed invisible dysplasia.
The group failed to reach consensus on the larger question of whether random biopsies are needed when endoscopists use high-definition white-light colonoscopy or chromoendoscopy. "We are increasingly moving beyond random biopsies because the technology now is such that we can visualize almost all dysplasia. But the American groups weren't quite ready to make a definitive statement although European groups have," explains Michael B. Wallace, M.D., an expert in advanced imaging and therapeutic endoscopy at Mayo Clinic's campus in Florida.
For now, he says, chromoendoscopy remains a supplement to the standard practice of random plus targeted biopsies, in large part due to a lack of widespread expertise in the technique. "A unique set of skills is required to recognize dysplastic lesions in IBD. A group of expert endoscopists has evolved who also have advanced skills in chromoendoscopy, but there aren't enough of them. There are also people within the IBD community who are strong advocates for the development of expertise through training tools such as freely available videos, but we don't have good data on the effectiveness of this yet," he says.
A Mayo Clinic study published in Inflammatory Bowel Diseases in 2013 does provide some data, however. For the study, researchers recruited six endoscopists from Mayo Clinic campuses in Arizona, Florida and Minnesota. The endoscopists, who were inexperienced with chromoendoscopy, underwent a short training session that consisted of viewing a teaching file of images and instruction in CE. They then performed surveillance colonoscopy with WLE followed by indigo carmine CE on 75 patients with long-standing ulcerative colitis.
The results showed excellent interobserver agreement for both WLE and CE images. Dysplasia detection rates with CE were superior to those with WLE, especially for flat lesions. "We showed that with minimal training, an individual can become competent after 15 procedures," Dr. Wallace says.
Michael F. Picco, M.D., and Dr. Wallace were lead study authors.
Other objections to chromoendoscopy include increased procedure time. But Dr. Wallace points out that newer methods of dye application have reduced the length of the procedure and that even more time will be saved by not having to perform random biopsies.
The more important point is the lack of clinical trials showing that chromoendoscopy is at least as good if not better than random biopsies at preventing cancer. "That's a big study that takes a long time, and we don't have that data yet," he says.
For more information
Bartel MJ, et al. Chromocolonoscopy. Gastrointestinal Endoscopy Clinics of North America. 2015;25:243.
Lane L, et al. SCENIC international consensus statement on surveillance and management of dysplasia in inflammatory bowel disease. Gastrointestinal Endoscopy. 2015;81:489.
Picco MF, et al. Procedure time and the determination of polypoid abnormalities with experience: Implementation of a chromoendoscopy program for surveillance colonoscopy for ulcerative colitis. Inflammatory Bowel Diseases. 2013;19:1913.