Published: February 22, 2012
Reviewed?by?Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine.
- In one study, mortality from colorectal cancer was markedly lower among patients who had undergone colonoscopy and had adenomas removed.
- In another study comparing colonoscopy and fecal immunochemical testing, the numbers of participants in whom colorectal cancer was detected were similar but more adenomas were found in the colonoscopy group.
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Deaths from colorectal cancer were only half as common among people who had precancerous intestinal polyps removed during colonoscopy as in the general population, researchers said.
In a study of 2,602 people who had adenomatous polyps removed and were followed for a median of 15.8 years, 12 died of colorectal cancer ? whereas data from the federal Surveillance, Epidemiology, and End Results database would predict 25 colorectal cancer deaths in this number of people, according to Ann G. Zauber, PhD, of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues.
The findings are some of the strongest evidence yet that colonoscopy with polyp removal not only reduces colorectal cancer incidence, but actually saves lives.
Meanwhile, preliminary results from a separate study suggested that frequent fecal immunochemical testing (FIT) is not an adequate substitute for colonoscopy if the goal is colorectal cancer prevention.
Spanish researchers conducting a randomized trial found polyp detection and removal rates were far lower in those screened by FIT, overwhelming a modestly higher ? and still very low ? screening acceptance rate among those offered FIT screening.
Both studies were published in the Feb. 23 issue of the New England Journal of Medicine.
In an accompanying editorial, two Norwegian researchers called colonoscopy ?an effective screening test when compliance is adequate.?
Michael Bretthauer, MD, PhD, of Oslo University, and Mette Kalager, MD, of Telemark Hospital in Skien, Norway, suggested that offering colonoscopy as a one-time ?triage? test at age 60 might be an attractive screening strategy.
The results could be used ?to classify persons as having a low risk of colorectal cancer (no adenomas detected) or a high risk (adenomas detected, particularly advanced ones), with strict surveillance for the latter group but no further screening for the former,? they wrote.
Bretthauer and Kalager noted that, in the study by Zauber and colleagues, it was not only the initial polypectomy but also ?strict surveillance? afterward that likely created the mortality benefit.
Zauber and colleagues were reporting long-term outcomes in the National Polyp Study (NPS), which enrolled patients undergoing colonoscopy at seven U.S. clinical centers.
It was structured as a randomized trial in which those with adenomatous polyps removed were rescreened either twice in the next three years (at years one and three) or just once at year three. Both groups were rescreened six years after polypectomy.
In the current report, however, death outcomes were reported only for both groups combined, and also for another group of 773 patients seen in NPS clinics who had nonadenomatous polyps removed. Deaths in study participants were determined from the National Death Index.
Also, Zauber and colleagues did not report outcomes of the surveillance colonoscopies, such as whether additional adenomatous or nonademonatous polyps were detected or removed.
On the basis of the SEER data, covering patients matched to NPS participants by age, sex, race, and other factors, the researchers estimated that 25.4 colorectal cancer deaths should occur in their adenoma population of 2,602.
Thus, the 12 deaths that did occur represented a 53% reduction in colorectal cancer mortality (ratio 0.47, 95% CI 0.26 to 0.80). The deaths occurred from six to 22 years after polypectomy, including four in the first nine years.
In the nonadenomatous cohort, with median follow-up of 16.5 years, there was one death within 10 years of polyp removal and none later on.
Limitations to the study included its reliance on the National Death Index and SEER data, and the possibility that the NPS clinics were not representative of colonoscopy providers generally.
The second study was reported by Antoni Castells, MD, PhD, of the Hospital Clinic in Barcelona, and colleagues. It involved early results from a projected 10-year study of biennial FIT versus one-time colonoscopy.
The trial is designed to compare mortality outcomes, but at this point ? just two years into the study ? Castells and colleagues reported only on acceptance of FIT and colonoscopy and the initial detection rates.
More than 50,000 people across Spain were randomized to be offered FIT, to be conducted every two years, or colonoscopy performed in the first year of the study.
The invitees were given no special incentives to participate other than the offer of an appointment at a local screening office, as well as information on colorectal cancer screening and the study?s rationale.
Rates of actual screening were low: 24.6% of those assigned to colonoscopy and 34.2% of those invited for FIT.
But although nearly 50% more FIT invitees received the screening, rates of detection of advanced and nonadvanced adenomas were much lower.
Among those receiving colonoscopy, advanced adenomas were found in 1.9%, versus 0.9 of the FIT-screened participants. Corresponding rates of nonadvanced adenoma detection were 4.2% with colonoscopy versus 0.4% with FIT.
Castells and colleagues indicated that the effect on mortality would have to await the final results of the study?s full 10 years.
But, in the editorial, Bretthauer and Kalager were skeptical that FIT could match, let alone better, the results of colonoscopy as the study goes on.
?Compliance data for the FIT group are only for the first round, and compliance with fecal screening has been shown to decrease over time,? they wrote.
Bretthauer and Kalager also pointed to the higher adenoma detection rates with colonoscopy, and the very low absolute detection rate with FIT ? which, they asserted, ?indicates that FIT is not a good test for detecting adenomas.?
The study by Zauber and colleagues was funded by the National Cancer Institute and the Cantor Colon Cancer Fund. All study authors declared they had no relevant financial interests.
The study by Castells and colleagues was funded by numerous government agencies and foundations in Spain. Eiken Chemical, Palex Medical, and Biogen Diagnostics supplied materials for FIT. No other relationships with commercial entities were reported.
Bretthauer reported receiving research support from Olympus Optical and Falk Pharma. Kalager indicated that she had no relevant financial interests.
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Source: http://profncampbell.wordpress.com/2012/02/23/removing-polyps-cuts-colorectal-cancer-deaths/
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