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Low-risk adenoma removal associated with reduced colorectal cancer mortality
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Patients who had low-risk adenomas removed demonstrated lower rates of long-term colorectal cancer mortality than those who had high-risk adenomas removed, according to results of a population-based study.
The low mortality rate associated with low-risk adenomas may obviate the need for post-colonoscopy surveillance in this population, researchers wrote.
Magnus Løberg, MD, of the department of health management and health economics at University of Oslo, and colleagues used Norway’s cancer registry and cause of death registry to assess colorectal cancer mortality among 40,826 adults who had colorectal adenomas removed between 1993 and 2007.
Patients with high-risk adenomas — or those with high-grade dysplasia, a villous component or a size ≥10 mm — underwent colonoscopy after 10 years, whereas those with three or more adenomas underwent colonoscopy after 5 years in compliance with Norwegian guidelines.
Patients with low-risk adenomas did not undergo surveillance.
Median follow-up was 7.7 years (maximum, 19 years).
Overall, 1,273 patients were diagnosed with colorectal cancer, and 383 deaths from colorectal cancer occurred. The observed colorectal cancer mortality rate was comparable to that of the general population (expected deaths, 398; standard mortality ratio [SMR]=0.96; 95% CI, 0.87-1.06).
Adenoma removal was associated with a reduced risk for colorectal cancer mortality among men (SMR=0.86; 95% CI, 0.74-1) but not women (SMR=1.06; 95% CI, 0.93-1.22).
Researchers determined 141 patients who died had low-risk adenomas removed. Data from the general population indicated that low-risk adenoma removal was associated with a reduced risk for death from colorectal cancer (expected deaths, 189; SMR=0.75; 95% CI, 0.63-0.88).
However, patients who had high-risk adenomas faced a greater colorectal cancer mortality risk (observed deaths, 242; expected deaths, 209; SMR=1.16; 95% CI, 1.02-1.31).
The risk for colorectal cancer mortality also was greater among patients with multiple adenomas (SMR=1.19; 95% CI, 1-1.43), a villous or tubulovillous growth pattern (SMR=1.26; 95% CI, 1.08-1.47), or a high grade of dysplasia (SMR=1.4; 95% CI, 1.15-1.72).
David Lieberman
“Our finding that the removal of low-risk adenomas reduces the risk of death from colorectal cancer over a period of 8 years to a level below the risk in the general population is consistent with the hypothesis that surveillance every 5 years after removal of low-risk adenomas may confer little benefit over less intensive surveillance strategies,” Løberg and colleagues wrote. “Furthermore, complications associated with colonoscopy are not trivial and might offset the benefit of surveillance.”
The data may indicate patients who have low-risk adenomas removed do not need to undergo surveillance, David Lieberman, MD, of the department of medicine and division of gastroenterology and hepatology at Oregon Health and Science University, wrote in an accompanying editorial.
“In the United States and abroad, there is now recognition that colonoscopic quality is variable and that poor quality is associated with higher rates of interval colorectal cancer,” Lieberman wrote. “If high-quality colonoscopy is performed, meaning excellent detection and complete removal of polyps, surveillance may not be needed for most patients with low-risk adenomas. If future studies — which include information about the quality of the examination — confirm that patients with low-risk adenomas would not benefit from surveillance, this would be an exciting development for patients and health care systems.”
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Disclosure: The study was funded in part by grants from the Norwegian Cancer Society, the Research Council of Norway and the U.S.–Norway Fulbright Foundation for Educational Exchange. Lieberman reports personal fees from Exact Sciences and Given Imaging outside the submitted work.
Perspective
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Ashwin R. Sama, MD
“An ounce of prevention is worth a pound of cure.” — Benjamin FranklinColorectal cancer screening by colonoscopy may decrease colorectal cancer incidence by removal of premalignant polyps and decrease mortality by early diagnosis of invasive colorectal cancer. It is unknown if continued surveillance of patients with adenomas has an effect on colorectal cancer incidence or mortality.
In this study, Løberg and colleagues used the Norwegian Cancer Registry to identify patients who had colorectal adenomas removed, and researchers obtained information on colorectal cancer incidence and mortality. It must be noted that the definition of high- and low-risk adenomas was modified due to limitations in cancer registry data entry. The Norwegian surveillance guidelines also differ from US guidelines, as high-risk patients had surveillance every 5 years to 10 years (as opposed to every 3 years by NCCN guidelines), and low-risk patients did not get surveillance colonoscopies (NCCN guidelines recommend every 5 years).
There was a decrease in colorectal cancer mortality in low-risk adenomas, likely due to interruption in the adenoma-to-carcinoma sequence. Colorectal cancer mortality was increased among patients with high-risk adenomas; this could be due intrinsic higher risk for colorectal cancer development in these patients or the development of “interval cancer.” A screening program is likely to decrease colorectal cancer mortality if it interrupts the adenoma–carcinoma sequence. If the interval between surveillance colonoscopies is too long, then it is likely that patients develop interval cancers. Quality and completeness of screening colonoscopy is a very important variable and is not reported.
Whether surveillance is effective in patients with “low-risk” adenomas or more frequent surveillance colonoscopies decrease mortality in “high-risk” adenomas is unknown and must be tested in future randomized studies.
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