Did you know that colorectal cancer is the second leading cause of cancer-related death both in the United States and worldwide? That makes colonoscopies a crucial screening tool for detecting polyps that can become colorectal cancer, so that the polyps can be removed before they can potentially become cancerous.
Spectrum anesthesiologist Aurora Quaye, MD, who works in the Department of Anesthesiology and Perioperative Medicine at Maine Medical Center, recently co-authored a study about the use of propofol based deep sedation during colonoscopies that has been published by the American Society of Anesthesiology. In it, she and her co-authors — Lynn Butterly MD, the Director of the New Hampshire Colonoscopy Registry (NHCR), William M. Hisey, MSc, Todd A. Mackenzie, PhD, Christina Robinson MS, Joe Anderson MD, Janelle Richard BA, and Dave Warters, MD, supported by the NHCR staff — analyzed the comprehensive, long-term data within the NHCR to determine whether the type of anesthesia used to sedate a patient during a colonoscopy has any discernable, significant impact on the detection of potentially pre-cancerous polyps.
In the U.S., the vast majority of colonoscopies are conducted with the patient under sedation. Two main types of sedation can be used: propofol sedation (propofol is an anesthetic that causes deep sedation, during which a patient is unlikely to have any conscious awareness) and conscious (moderate) sedation (in which a person is asleep but wakes when spoken to or touched).
So far, it has been unclear whether colonoscopies are more successful in finding polyps while using propofol or moderate sedation. Other studies have been conducted to investigate the question, but with conflicting results and important limitations.
Dr. Quaye, Dr. Butterly, and their co-investigators conducted a retrospective cohort study using data from the New Hampshire Colonoscopy Registry, a statewide, population-based registry which was founded 20 years ago at Dartmouth Hitchcock Medical Center.
Between 2015 and 2020, the New Hampshire Colonoscopy registry included 54,063 colonoscopies that fit the researchers’ pre-determined parameters (in other words, including only colonoscopies appropriate for the study). Data used for analysis included detailed patient, procedure, endoscopist, sedation, and pathology data.
The researchers included patients older than age 50 (the age previously recommended to start colorectal cancer screening; age 45 is the currently recommended age) who had received screening or surveillance colonoscopies between January 1, 2015, and February 28, 2020. In screening examinations, the patients have no previous personal history of precancerous colon polyps or colorectal cancer. When patients do have a previous history of polyps or colorectal cancer, it is called a surveillance colonoscopy.
Quaye, Butterly and the NHCR team also wanted to determine whether the type of sedation used for a colonoscopy was associated with the type of polyp gets detected, and with what frequency. Two major groups of polyps are considered to be the precursors of colorectal cancer: adenomas and serrated polyps.
Adenomas are thought to be the precursors of 70% of colorectal cancer (CRC), and serrated polyps are thought to be the precursors for up to 30% of CRC. Serrated polyps are more difficult to detect during colonoscopy because they tend to be flatter and are often covered with a mucus cap, causing them to blend into the folds of the colon. Detected polyps are painlessly removed during colonoscopy, preventing them from potentially developing into colorectal cancer in the future.
In this study, Dr. Quaye and her co-investigators discovered that propofol-based deep sedation was associated with higher detection of the serrated lesions, supporting the hypothesis that propofol may have differential effect in improving the detection of more difficult to identify lesions.
Part of their process involved researching a subset of the larger NHCR database of colonoscopies. They removed any endoscopists and facilities from the study that reported using propofol for almost every colonoscopy (more than 95% of the time) or almost never (less than 5% of the time). That left 18,998 colonoscopies performed at the subset of facilities that routinely used both sedation options.
Among those 18,998 colonoscopies, serrated polyps were detected more often among patients receiving propofol sedation (30.3%; 1,410 of 4,661) versus moderate sedation (25.7%; 3,690 of 14,337).
In other words, (after further adjustment for patient and endoscopist factors at these facilities), propofol sedation was associated with a 13% higher likelihood of detecting serrated polyps compared to moderate sedation. However, the study found no difference in the likelihood of detecting adenomas at these same facilities. (That is, they saw no difference in how many adenomas were detected when propofol was used for sedation).
This difference could have important implications for screening and surveillance colonoscopies. The study’s authors write:
“Although polyps are more common in men, women over the age of 50 years are more likely to develop premalignant lesions in the proximal colon, where serrated lesions are more common. As research continues to evolve, identifying patient populations at greatest risk for serrated polyp development and targeted strategies aimed at improving detection of these high-risk lesions will be essential.”
“Our study provides preliminary evidence that propofol-based sedation may play an important role in ensuring optimal colonoscopy polyp detection. Additional studies to clarify the effectiveness of propofol will guide understanding of best practices for colorectal cancer prevention.”
“As propofol use for colonoscopy continues to grow nationally, there is meaningful debate regarding the effectiveness of this practice. Our study provides evidence that propofol use may be associated with increased serrated polyp detection; since these lesions may be the precursors for up to 30% of colorectal cancers, improving their detection may be of substantial benefit.”
We at Spectrum would like to congratulate Dr. Quaye and her co-investigators for their findings, which could lead to improved colorectal cancer detection and treatment – and improved patient health – everywhere.
