Posted on 09-06-2011
Most people who are at average risk for colorectal cancer and who have a negative colonoscopy probably do not need another screening colonoscopy for at least 20 years, if they need one at all, German researchers suggest. However, screening experts beg to differ.
In a study published online August 29 in the Journal of Clinical Oncology, Hermann Brenner, MD, MPH, from the University of Heidelberg, Germany, and colleagues write that screening intervals could be longer than the 10 years recommended by current guidelines "in most cases, perhaps even among men and people with a family history of [colorectal cancer], but probably not among current smokers."
However, David A. Johnson, MD, past president of the American College of Gastroenterology (ACG) and coauthor of the ACG and the American Cancer Society colon cancer screening guidelines, counters that it would be entirely premature to extend the 10-year screening interval on the basis of 1 study.
"I would be very apprehensive about anybody taking the information from this study and jumping to a conclusion that colonoscopy screening can be deferred for 20 years. Certainly, from 1 study, that would be an inappropriate conclusion," Dr. Johnson, who is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, told Medscape Medical News.
In their paper, Dr. Brenner and his team report that the 10-year screening interval is recommended because of the absence of strong evidence from long-term studies, and they note that in general, empirical evidence for overall and risk-group-specific definitions of screening intervals is sparse.
In their population-based case-control study, the researchers recruited 1945 patients with colorectal cancer and 2399 control subjects from 22 hospitals and population registers in the Rhine-Neckar region of Germany from 2003 to 2007.
They collected data on history of colonoscopy, age, sex, years of education, history of colorectal cancer among first-degree relatives, smoking, use of nonsteroidal anti-inflammatory drugs, use of hormone replacement therapy, and previous participation in a general health screening examination.
After controlling for these factors, the researchers found that a previous negative colonoscopy was associated with a strongly reduced risk for colorectal cancer (adjusted odds ratio, 0.19; 95% confidence interval [CI], 0.15 to 0.23), and that very low risks continued for 20 years or more.
The researchers report that adjusted odds ratios were very low for left-sided and right-sided cancers for more than 20 years after a negative colonoscopy.
"Our results suggest that, despite not being preventive by itself, a negative colonoscopy is of great clinical value, because people with such a result can be assured of being at a low risk of [colorectal cancer] for a long time," the authors write. "Furthermore, the finding of sustained low risk for 20 years and beyond after a negative colonoscopy suggests that a screening colonoscopy might not need to be repeated after 10 years as was previously recommended."
The researchers conclude by suggesting that the possibility of extending screening intervals beyond 10 years, "perhaps even among people with a positive family history," could make colonoscopy screening more cost effective and reduce complications associated with the procedure.
Extending the interval could also make population-wide colonoscopic screening feasible in countries that have limited resources for high-quality colonoscopies, they add.
Colon Cancer Can Occur Even Within the 10-Year Interval
In an interview with Medscape Medical News, colonoscopy expert Dr. Johnson explained that "the interval of 10 years was developed primarily because of what we know about the development of polyps and their progression into cancer."
"The idea that it could be lengthened would certainly be challengeable, in particular when you look at several recent studies that have shown that there have been interval cancers in patients who have had a colonoscopy, " he said.
Such interval cancers were probably the result of poor-quality colonoscopies, Dr. Johnson said. "We feel very strongly that those interval cancers developed because of lesions that were missed because the examiners weren't doing as good a quality exam as set by current standards."
The study by Dr. Brenner and colleagues "is an interesting case-control study and has many limitations to extrapolation," he added. "Certainly it would be premature to base any extension of screening guidelines [on the basis of] this study alone. Prospective studies with appropriate stratification of risks would be warranted. This study should not challenge clinical practice."
Weighing in with his opinion, John M. Inadomi, MD, chair of the American Gastroenterological Association Clinical Practice and Quality Management Committee, and Cyrus E. Rubin Professor and head of gastroenterology at the University of Washington School of Medicine, Seattle, noted that the focus of colonoscopy screening studies should be on getting individuals to be screened at least once in their lifetime, not on the issue of repeat screening in low-risk individuals.
Referring to Dr. Brenner and colleagues, he told Medscape Medical News that "this group has published a multitude of studies using this dataset, and they do not have a consistent message.... They published a highly cited study in which they concluded that colonoscopy protected against left-sided or distal but not right-sided or proximal cancers or advanced adenomas [J Natl Cancer Inst. 2010;102:89-95]. However, they subsequently published a seemingly contradictory study concluding that both right- and left-sided colon cancer was prevented by colonoscopy [Ann Intern Med. 2011;154:22-30]. Hard to know how you could prevent cancer but not the combination of cancer and advanced adenomas in the proximal colon," he said.
"Now they publish this study using the same data and conclude that after a negative colonoscopy the risk of colon cancer is significantly lower than if you never had a colonoscopy. I think this is kind of an obvious result," he said.
Dr. Inadomi added that colonoscopy is not perfect, "especially when it is done by endoscopists who have low adenoma detection rates.... If I knew the quality of the colonoscopy was excellent and that the risk of an aggressive neoplastic lesion was low, I would suggest a longer interval between screening colonoscopies."
Dr. Brenner has disclosed no relevant financial relationships.
J Clin Oncol. Published online August 29, 2011.
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