Blue-dye tablet taken during colonoscopy bowel prep boosts polyp detection rate

Last Updated: 2018-05-28

By Megan Brooks

NEW YORK (Reuters Health) - Swallowing a tablet of delayed-release methylene blue during bowel preparation for colonoscopy increases detection of adenomas, particularly hard-to-detect ones that are flat or subtle, according to results of a randomized, placebo-controlled trial.

"Our study, which used the highest standard of care, allowed gastroenterologists to better detect and remove difficult-to-see polyps, which has great implications for further preventing this disease," Dr. Alessandro Repici, director of endoscopy at Humanitas University Medical School in Milan, Italy, said in a news release.

"If an adenoma is not detected, we would consider that a missed adenoma, and these missed adenomas are thought to be the ones that go on to develop cancer," said Michael Wallace, director of digestive disease research at Mayo Clinic in Jacksonville, Florida, during a briefing May 21 ahead of study presentation June 3 at Digestive Disease Week (DDW).

"An oral delayed-release methylene blue tablet taken during the standard bowel preparation for colonoscopy has the potential to increase the adenoma detection rate and could assist in the early detection and prevention of colorectal cancer," said Dr. Wallace, who also worked on the study.

The study included more than 1,200 patients (age, 50 to 75 years) scheduled for colorectal-cancer screening or surveillance colonoscopy at 20 centers worldwide. They were randomly allocated to take a tablet containing 100 mg or 200 mg methylene blue or placebo during the normal bowel-prep regimen the day before the procedure. The 100-mg group was only for masking purposes at the request of the FDA and was excluded in the statistical analysis.

A total of 626 patients (52%) had at least one adenoma or carcinoma detected during colonoscopy.

The adenoma-detection rate (ADR) increased by nearly 9 percentage points in the full-dose blue-dye arm compared with the placebo arm (56% vs. 48%; odds ratio, 1.41; 95% confidence interval, 1.09 to 1.81), Dr. Wallace reported.

"While 9% may not seem like a large number, it's actually very clinically significant," he said. "There have been several major trials . . . that showed that for every 1% increase in the absolute adenoma detection rate, there was a corresponding 3% decline in the incidence of colorectal cancer and a 5% decline in colorectal-cancer deaths."

In addition, more flat and small lesions (less than 5 mm) were found in patients who took the full-dose methylene-blue tablet (37% vs. 33%; OR, 1.36; 95% CI, 1.01 to 1.83). The false-positive rate was 23% with the blue dye and 30% with placebo. Aside from the expected blue feces and urine discoloration, less than 6% of patients experienced mild adverse effects when taking the tablet.

Utilizing blue dye to boost adenoma detection is not a new concept, Dr. Wallace told the briefing, "with more than a decade of clinical trials showing its benefit. The fact that this technology comes in a tablet form is a step forward."

Previously, he explained, the blue dye had to be mixed by the providers onsite. "It's difficult to mix onsite and there has been some variability in the ability to obtain blue dye at many centers throughout the world. Also, when it was mixed onsite, it had to be sprayed during the colonoscopy itself and the spraying through the colonoscope could be imprecise, time consuming and generally localized and as a result it was never widely adopted," said Dr. Wallace.

"With the tablet form, the majority of the dye is released in the colon prior to the colonoscopy. In most cases, the dye specifically stains the polyp itself," said Dr. Wallace.

The study was funded by Cosmo Pharmaceuticals, which developed the tablet. Dr. Repici and Dr. Wallace are consultants for the company.

SOURCE: https://bit.ly/2s8SAze

Digestive Disease Week (DDW) 2018.