[Comment] Colonoscopy, cancer prevention, and the new arithmetic of benefit

Colonoscopy, cancer prevention, and the new arithmetic of benefit
Affiliations & Notes
Division of Gastroenterology, Department of Medicine, NYU Grossman School of Medicine, New York, NY 10016, USA
Article Info
Publication History:
Published May 4, 2026
DOI: 10.1016/S0140-6736(26)00794-4 External LinkAlso available on ScienceDirect External Link
Copyright: © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
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OkFor more than two decades, colonoscopy has been promoted as the gold standard for colorectal cancer screening. Policy makers and professional societies have largely accepted observational data and modelling estimates that suggest that colonoscopy cuts colorectal cancer incidence and mortality by at least 50%.1 Against this backdrop of strong belief but insufficient randomised evidence, the NordICC randomised clinical trial of colonoscopy screening versus usual care for the primary endpoints of colorectal cancer incidence and mortality has been uniquely important.2 The study's 13-year results compel a recalibration of what colonoscopy can—and cannot—achieve at the population level.
References
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US Preventive Services Task Force
Screening for colorectal cancer: US Preventive Services Task Force recommendation statement
JAMA. 2021; 325:1965-1977
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Effect of colonoscopy screening on risks of colorectal cancer and related death
N Engl J Med. 2022; 387:1547-1556
3.
Kaminski, MF ∙ Kalager, M ∙ Løberg, M ∙ et al.
Long-term effects of colonoscopy screening on colorectal cancer incidence and mortality: a multicountry, population-based randomised controlled trial
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published online May 5. https://doi.org/10.1016/S0140-6736(26)00508-8
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Facts Only

* Colonoscopy is promoted as the gold standard for colorectal cancer screening.
* Observational data and modeling estimates suggest colonoscopy cuts colorectal cancer incidence and mortality by at least 50%.
* The NordICC randomized clinical trial compared colonoscopy screening versus usual care for colorectal cancer incidence and mortality.
* The NordICC study provided 13-year results regarding the effects of colonoscopy screening.
* The US Preventive Services Task Force issued a recommendation statement regarding colorectal cancer screening.
* A multicountry, population-based randomized controlled trial examined the long-term effects of colonoscopy screening on colorectal cancer incidence and mortality.
* A randomized controlled trial investigated the long-term effects of once-only flexible sigmoidoscopy screening after 17 years of follow-up.
* A long-term follow-up of the Italian Flexible Sigmoidoscopy Screening Trial was conducted.
* The effects of screening compliance were examined on long-term reductions in all-cause and colorectal cancer mortality.

Executive Summary

Colonoscopy is promoted as the gold standard for colorectal cancer screening. Observational data and modeling estimates suggest that colonoscopy reduces colorectal cancer incidence and mortality by at least 50%. The NordICC randomized clinical trial, comparing colonoscopy screening versus usual care, provided crucial 13-year results that necessitate a recalibration of the ability of colonoscopy to achieve benefits at the population level. This finding emerged against a backdrop of strong professional belief but insufficient randomized evidence. Multiple long-term follow-up studies and trials, such as those involving flexible sigmoidoscopy screening, have explored the effects of different screening modalities, including the influence of screening compliance on mortality reductions. The context highlights the ongoing tension between established professional consensus based on observational findings and the demand for definitive evidence provided by rigorous randomized controlled trials.

Full Take

The shift from accepting observational modeling to demanding randomized evidence reflects a systemic tension in public health knowledge: the conflict between expert consensus and empirical rigor. The statement that observational data suggests a 50% reduction sets a high bar, but the necessity of the NordICC trial underscores the danger of mistaking correlation for causation. This pattern highlights how powerful established belief structures (the "gold standard") can resist necessary recalibration until formalized randomized testing is conducted. The implication is that authority, whether professional or scientific, must be continually subordinated to the most robust evidence. Questions arise about the weighting given to modeling estimates versus definitive trial outcomes, and who controls the narrative when observational acceptance precedes the gold standard of randomized proof. The cost-benefit of adopting screening protocols is dependent on fully understanding the uncertainty introduced by relying on estimates rather than definitive outcomes.