# Long term effects of once-only flexible sigmoidoscopy screening after 17 years of follow-up

Source: https://onco.cc/key-papers/paper-atkin-flexible-sigmoidoscopy-17-year-follow-up-lancet-2017/  
OnCo record `paper-atkin-flexible-sigmoidoscopy-17-year-follow-up-lancet-2017` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Seventeen years after a single flexible sigmoidoscopy, the protection was still there: a quarter fewer bowel cancers and a third fewer deaths.

## Summary

Atkin, Wooldrage, Parkin and colleagues extended the UK Flexible Sigmoidoscopy Screening Trial, run between November 1994 and March 1999, to a median 17.1 years of follow-up in 170,034 people: 112,936 controls and 57,098 in the intervention group, of whom 40,621 (71 percent) were screened.

Colorectal cancer was diagnosed in 1,230 people in the intervention group and 3,253 in the control group, and 353 against 996 died of it. The protection from one examination did not wane over the whole observation period, which is the finding that matters for how often screening endoscopy needs to be repeated.

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Tags: colorectal-evidence
- Journal: The Lancet
- Year: 2017
- DOI: 10.1016/S0140-6736(17)30396-3
- Authors: Atkin W, Wooldrage K, Parkin DM, et al.
- Findings: Intention to treat at 17.1 years: incidence reduced 26 percent (hazard ratio 0.74, 95 percent CI 0.70 to 0.80) and mortality 30 percent (0.70, 0.62 to 0.79), both p<0.0001.; Per protocol: incidence 35 percent lower (0.65, 0.59 to 0.71) and mortality 41 percent lower (0.59, 0.49 to 0.70).; A single flexible sigmoidoscopy continued to protect for at least 17 years.
- What it means: Durability is what makes endoscopic screening cost-effective: one procedure at 55 buys nearly two decades of protection, which is the argument for long intervals rather than frequent tests.
- Caveats: Same self-selected, screening-willing population as the 2010 report.; Protection is for distal disease only; the trial cannot speak to the right colon.

## Sources

- Lancet 2017: https://doi.org/10.1016/S0140-6736(17)30396-3
- PubMed: https://pubmed.ncbi.nlm.nih.gov/28236467/
- Europe PMC full text (PMC6168937): https://europepmc.org/article/MED/28236467

## Connected records

- key papers: [Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial](https://onco.cc/key-papers/paper-atkin-once-only-flexible-sigmoidoscopy-lancet-2010/)
- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/)
- fronts: [Early Detection & Screening](https://onco.cc/fronts/early-detection/), [Prevention & Risk](https://onco.cc/fronts/prevention/)
- technologies: [Colorectal cancer screening (colonoscopy, FIT, stool DNA, blood)](https://onco.cc/technologies/colorectal-screening/)
- terms: [Endoscopy (EGD, EUS, ERCP)](https://onco.cc/terms/endoscopy/)
- institutions: [Cancer Research UK](https://onco.cc/institutions/cruk/), [National Institute for Health and Care Excellence](https://onco.cc/institutions/nice/)
- bottlenecks: [The hardest cancers are found late](https://onco.cc/bottlenecks/b-early-detection/)
- journals: [The Lancet](https://onco.cc/journals/lancet/)
- roadmaps: [Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation](https://onco.cc/roadmaps/colorectal-roadmap/)
- ideas: [UK gap: match endoscopy capacity and quality to the faecal immunochemical test thresholds the NHS has already set](https://onco.cc/ideas/idea-crc-uk-colonoscopy-capacity-and-fit-threshold/)

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