Colonoscopy can significantly reduce the incidence of colorectal cancer (CRC) and specific CRC-related mortality, a large case-control study shows.
Using Veterans Affairs (VA)–Centers for Medicare & Medicaid Services data, the study investigators show that colonoscopy was associated with a 61% reduction in CRC mortality in veterans with left-sided as well as those with right-sided disease.
The study, led by Charles J. Kahi, MD, of Roudebush VA Medical Center in Indianapolis, Indiana, and Heiko Pohl, MD, of White River Junction VA Medical Center in Vermont, was published online March 12 in the Annals of Internal Medicine.
"Our estimates of reductions in CRC mortality are similar to those from different health care settings, which supports the validity of our findings," the study authors say.
"These findings confirm that performing colonoscopies and colon cancer screening reduces colorectal cancer mortality and improves outcomes for patients," said Jeffrey Meyerhardt, MD, MPH, when approached for comment.
Meyerhardt is an American Society of Clinical Oncology expert in gastrointestinal cancers and clinical director of the Gastrointestinal Cancer Center at Dana-Farber Cancer Institute in Boston, Massachusetts.
"Colonoscopy, primarily screening colonoscopy, saves lives," he told Medscape Medical News.
Many clinicians appear to share this view. The use of colonoscopy has increased exponentially since 2001, when the procedure was included as a Medicare benefit. In 2007, colonoscopy was endorsed by the Veterans' Health Administration (VHA) as a primary CRC screening option for patients aged 50 years and older. Currently, it is estimated that up to 14 million Americans undergo colonoscopy annually.
Despite this, evidence from randomized controlled trials demonstrating that colonoscopy reduces CRC mortality is lacking, the investigators say. Previous study findings are inconsistent, possibly owing to differences in operator skill. "Reducing variability in colonoscopy effectiveness, particularly against right-sided CRC, is critical for effective prevention of CRC," the researchers write.
In addition, there is still a question mark over whether colonoscopy is a more effective screening tool than fecal immunochemical testing (FIT), they comment.
These findings "do not answer the question of whether colonoscopy is the best CRC screening test," they write. "From the standpoint of any large integrated health care system, this issue requires not only comparison of effectiveness at the patient level but also considerations of cost, cost-effectiveness, resource availability and allocation, and patient adherence."
Screening with FIT is being compared to colonoscopy-based screening in four ongoing randomized controlled trials. The VA's Colonoscopy Versus Fecal Immunochemical Test in Reducing Mortality From Colorectal Cancer (CONFIRM) study is one of them.
"These trials will provide more definitive information on which test should be the first-line option for CRC screening in the VHA," the study authors say.
In the study, 4964 veterans with CRC were identified between January 1, 2002, and December 31, 2008. All had received a diagnosis of CRC by age 50 years or older and had died of CRC by age 52 years or older.
These case patients were matched in a 4-to-1 ratio for sex and age with 19,856 control patients who did not have a history of CRC. The two groups were also matched by VA facility to " 'level the playing field' for geographic accessibility to health care," the study authors say.
The mean age of the study population was 71.7 years, and 99.3% were men.
In case veterans, exposure to colonoscopy was determined from 1997 to 6 months before CRC diagnosis. Odds ratios were calculated after adjusting for potential CRC risk confounders. These included race, socioeconomic status, comorbidities such as diabetes and ischemic heart disease, cigarette smoking, the use of nonsteroidal anti-inflammatory drugs, and a family history of CRC.
Mean comorbidity scores on the Charlson Comorbidity Index were significantly higher for case veterans than for control patients, and case veterans had significantly less exposure to colonoscopy (13.5% vs 26.4% P < .001).
Of 688 case patients, 67.8% underwent colonoscopy for diagnostic indications, as did 60.9% of 5250 control patients. In addition, 15.5% of case veterans and 21.3% of control patients underwent screening colonoscopy, and 16.0% of case patients and 17.8% of control patients underwent surveillance colonoscopy (P < .001).
Among case veterans, the median time between colonoscopy and CRC diagnosis was 43.5 months.
Cancer was categorized as either right-sided, which included the cecum, the ascending colon, the hepatic flexure, or the transverse colon, or left-sided, which included the splenic flexure, the descending colon, the sigmoid colon, or the rectum.
The survival benefit was more pronounced in those with left-sided cancer than in those with cancer in the right colon (72% vs 46%; adjusted odds ratio [OR], 0.28 and 0.54, respectively).
The same trends were seen in a subgroup of veterans who underwent screening colonoscopy (adjusted overall OR, 0.30: 0.20 for left-sided cancer, and 0.48 for right-sided cancer). These findings did not change when the interval between CRC diagnosis and colonoscopy exposure was varied.
Important Risk Reduction
"These data further support the important CRC risk reduction provided by colonoscopy," said David A. Johnson, MD, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, who was approached for comment.
Placing an emphasis on high-level performance, as defined by national quality endoscopy metrics and benchmark electronic reporting to national registries, such as GIQuIC, "will help further refine risk reduction," he told Medscape Medical News. "Clearly we recognize the importance of the high-quality endoscopist, defined by a high level of adenoma detection."
Landmark studies from Germany have shown a significant correlation with interval CRC risk reduction if the colonoscopy is performed by a gastroenterologist with a high adenoma detection rate (ADR), Johnson noted. In addition, a US study has shown that for every 1% increase in ADR, the risk for CRC incidence and CRC-related morality is reduced by 3% and 5%, respectively.
National guidelines set the minimum threshold for quality for ADR on initial screening colonoscopy at 25% (30% for men and 20% for women), Johnson pointed out. Almost all of the VA study participants were male, however, and the ADR was not reported. "It would be an important quality discriminant for those who developed CRC post colonoscopy," he said.
Interval CRC cases are often located in the right colon and in areas where prior polypectomy has been performed. They have also been associated with the serrated polyps pathway, Johnson explained.
The current study is based on 2002-2010 data, and the prevalence of serrated lesions has continued to increase since then, he noted. Recognizing these subtle, flat polyps are "critical to ensure adequate resection," he added.
The current analysis mirrored the trend in colonoscopy use in the larger US population, in which the proportion of patients who underwent colonoscopy for a screening indication increasing steadily from 8.0% in 2001 to 32.6% in 2007 or later.
The study was funded by the US Department of Veterans Affairs. Dr Kahi and Dr Pohl have disclosed no relevant financial relationships. Study coauthor Douglas J. Robertson, MD, reports a relationship with Medtronic. The other study coauthors have disclosed no relevant financial relationships. Dr Johnson has or has had financial ties to Pfizer Inc, Epigenomics, WebMD, CRH Medical, and Medtronic. Dr Meyerhardt reports relationships with Chugai Pharma, Ignyta, and Roche/Genentech.
Ann Intern Med. Published online on March 12, 2018. Abstract
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Cite this: Colonoscopy Significantly Reduces CRC Deaths - Medscape - Mar 14, 2018.