A Single Flexible Sigmoidoscopy Screening Tied to Long-Term Protection Against Colorectal Cancer

By Marilynn Larkin

November 22, 2021

NEW YORK (Reuters Health) - In adults ages 55 to 64, a single flexible sigmoidoscopy (FS) screening is associated with a substantial reduction in colorectal cancer (CRC) incidence and mortality, with a protective effective lasting up to 18 years, researchers say.

"The findings support the hypothesis of a plateau in the adenoma incidence in the distal colon at around age 60," Dr. Carlo Senore of University Hospital Città della Salute e della Scienza in Turin told Reuters Health by email. "The strong protective effect of this screening modality can be explained by its ability to detect and excise all the lesions which might develop into invasive CRC."

"Consistent with previous reports, our study confirms that the protective effect of a single FS screening is maintained up to 18 years," he said. "The recommendation to repeat FS at five-to-10-year intervals should be revised, as the additional benefit of repeating the test is likely negligible, if any."

"The benefit-to-harm ratio of this strategy would be improved when adopting a once-in-a-lifetime approach," he added, "because of the substantial reduction in the burden associated with screening. as well as the reduction in healthcare costs."

As reported in Annals of Internal Medicine, Dr. Senore and colleagues assessed CRC incidence and mortality over the long term after a single FS screening by analyzing data from a parallel randomized controlled trial in which patients from six centers in Italy were assigned to once-only FS or usual care.

Participants ages 55 to 64 were recruited from 1995 to 1999 and followed until 2012 (incidence) and 2014 to 2016 (mortality).

A total of 34,272 individuals were included in the analysis; 9,911 participants had screening in the intervention group. Median follow-up was 15.4 years for incidence and 18.8 years for mortality.

CRC incidence was reduced by 19% (rate ratio, 0.81) in the intention-to-treat (ITT) analysis, and by 33% (RR, 0.67) in the per protocol (PP) analysis.

Similarly, CRC mortality was reduced by 22% (RR, 0.78) in the ITT analysis and by 39% (RR, 0.61) in the PP analysis.

CRC incidence was significantly reduced among both men and women, but CRC mortality was significantly reduced only among men (ITT RR, 0.73), not among women (ITT RR, 0.90).

Further, the incidence of distal CRC was significantly reduced by 30% (RR, 0.70) overall, whereas no effect was noted for proximal CRC (RR, 1.03).

The authors state, "Although its protective effect for proximal CRC is limited, the 30% reduction in overall CRC risk represents a milestone that can be achieved in the general population with sustainable costs and equity. Promoting integration with primary prevention interventions would further increase the preventive effect of FS screening."

Dr. Michael Bretthauer of the University of Oslo and University of Tromso in Norway, coauthor of a related editorial, commented in an email to Reuters Health, "With this trial, all four large-scale RCTs worldwide have now been concluded; a 20-year era is over."

"Based on these findings, the current guideline recommendation of repeating sigmoidoscopy every five years may be extended to longer intervals, reducing costs and burden," he said. "A caveat is that the effects are larger in men as compared to women, so I'm not sure if this screening test is best for women."

SOURCE: https://bit.ly/3HwjwOy and https://bit.ly/3oKqRBz Annals of Internal Medicine, online November 8, 2021.