Gastroenterology centers with higher adenoma detection rates (ADR) with the use of flexible sigmoidoscopy (FS) had a lower long-term colorectal cancer incidence and lower CRC mortality among its patients, according to a new study.
Detection and removal of polyps during colonoscopy screening is vital to the prevention of CRC, and previous research has shown that centers with higher detection rates are associated with lower rates of CRC diagnosis within 3-5 years after a negative screen.
In Clinical Gastroenterology and Hepatology, researchers led by Amanda J. Cross, PhD, a professor of cancer epidemiology at Imperial College London, published an analysis of the UK Flexible Sigmoidoscopy Screening Trial, which found that FS screening between the ages 55 and 64 led to a 35% reduction of CRC incidence and a 41% reduction in CRC over a mean follow-up 17.1 years. The screening program had no apparent effect on incidence and mortality of proximal cancers. The researchers speculated that this was because few patients underwent proximal examination during follow-up colonoscopy.
“Considering only 5% of participants were referred for follow-up colonoscopy and 4% were referred for surveillance, we conclude that the improved detection of adenomas at FS has a measurable impact on long-term distal CRC outcomes, even when there is infrequent colonoscopy use. It is possible that high detectors also were more adept at polypectomy than intermediate or low detectors, and achieved more complete resection of detected lesions,” the authors wrote.
The researchers analyzed data from 38,550 patients who underwent screening at 14 U.K. hospitals, between 1994 and 1999. A single endoscopist was responsible for nearly all FS screens performed at each participating hospital.
The mean patient age was 60 years, and 49% were male. The researchers calculated ADRs for each center using the percentage of patients who had at least one adenoma detected during screening, which included any distal adenomas discovered during follow-up colonoscopy.
The ADR overall was 12%. The researchers used multivariate logistic regression to rank individual centers as having high (15%; five centers), intermediate (12%; four centers), or low (9%; four centers) detection rates.
There was a strong association between detection rates of small adenomas and a center’s ADR (P < .001), but not for large or advanced adenomas. In the high-detector group, 6.2% of patients screened were referred to colonoscopy versus 4.5% in the intermediate group and 4.5% in the low group. About half of colonoscopies were conducted by the same endoscopist who performed FS.
During follow-up, the distal CRC incidence was 1.5% in the high ADR group, 1.4% in the intermediate group, and 1.7% in the low group, and mortality rates were 0.4%, 0.4%, and 0.5%, respectively.
Compared with unscreened controls, risk of distal CRC was lowest among individuals who underwent screening in the high ADR group (hazard ratio, 0.34; 95% confidence interval, 0.27-0.42), followed by the intermediate group (HR, 0.46; 95% CI, 0.36-0.59), and the low ADR group (HR, 0.55; 95% CI, 0.44-0.68; P < .05 for all).
Compared with unscreened controls, CRC mortality was lower among individuals who underwent screening in the high ADR group (HR, 0.22; 95% CI, 0.13-0.37), followed by the intermediate group (HR, 0.30; 95% CI, 0.17-0.55), and the low ADR group (HR, 0.54; 95% CI, 0.34-0.86; P < .05 for between group differences).
All-site CRC incidence followed similar trends, with the lowest risks in the high ADR group (HR, 0.58; 95% CI, 0.50-0.67), followed by intermediate ADR (HR, 0.65; 95% CI, 0.55-0.77) and low ADR groups (HR, 0.72; 95% CI, 0.61-0.85; between group differences not statistically significant).
All-site CRC mortality was lowest in the high ADR group (HR, 0.52; 95% CI, 0.39-0.69), followed by the intermediate group (HR, 0.53; 95% CI, 0.38-0.73), and the low ADR group (HR, 0.68; 95% CI, 0.51-0.92; between-group differences not statistically significant).
The number needed to screen (NNS) to prevent one CRC diagnosis was 78 in the high ADR group (95% CI, 61-106), 103 in the intermediate group (95% CI, 74-171), and 125 in the low ADR group (95% CI, 82-256). The NNS to prevent one CRC death was 226 (95% CI, 159-387), 247 (95% CI, 165-490), and 349 respectively (95% CI, 192-1,904).
However, the researchers also pointed out that efforts to increase ADR could result in more complications, such as perforations or gastrointestinal bleeding, as well as more frequent diagnosis and recommended surveillance for diminutive adenomas.
The study is limited by the fact that endoscopists were either gastroenterologists or surgeons and the study population was made up of individuals who desired screening.
The UK Flexible Sigmoidoscopy Screening Trial was funded by the UK Medical Research Council and the National Institute for Health Research. The authors disclosed no conflicts of interest.
