Smoking cessation

Avoid

5 studies · 1 recommendation

Last updated: February 27, 2026

Avoid5 studies

Smoking significantly increases colorectal cancer risk and undermines post-treatment surveillance accuracy

Across 5 studies encompassing over 200,000 participants, smoking consistently elevated colorectal cancer risk and complicated follow-up care. A Norwegian cohort of 35,525 women attributed 18.7% of colon cancer cases to smoking — the single largest modifiable risk factor. A Japanese case-control study (685 cases, 778 controls) found heavy smokers (≥400 cigarette-years) faced 60% higher rectal cancer risk (OR 1.60, 95% CI 1.04–2.45). A broader Norwegian cohort of 170,000 women confirmed smoking as a dominant lifestyle driver of colorectal cancer incidence. Beyond prevention, a systematic review of 52 studies (9,717 participants) demonstrated that smoking renders CEA surveillance unreliable, producing frequent false positives and leading researchers to recommend against CEA monitoring in continuing smokers entirely. Smoking cessation reduces both incidence risk and ensures effective post-diagnosis monitoring.

Evidence

A healthy lifestyle index and cancer: Using a multifactor lifestyle exposure to estimate cancer incidence and survival among Norwegian women

Authors: Chen, Sairah Lai Fa

Published: August 17, 2023

In the Norwegian Women and Cancer Study cohort of approximately 170,000 women, higher HLI scores — with non-smoking as a component — were associated with lower colorectal cancer risk. Smoking was identified as particularly strong in driving several of the observed associations between lifestyle and cancer incidence. The study used Cox proportional hazard models and restricted cubic splines, concluding that smoking avoidance should be a priority throughout all adult ages.

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The burden of colon cancer attributable to modifiable factors—The Norwegian Women and Cancer Study

Authors: Borch, Kristin Benjaminsen, Laaksonen, Maarit A., Licaj, Idlir, Lukic, Marko, Rylander, Charlotta, Weiderpass, Elisabete

Published: August 22, 2022

In a cohort of 35,525 Norwegian women from the NOWAC study, the population attributable fraction of colon cancer due to ever smoking was 18.7% (95% CI 4.7%-30.6%), making it the largest single modifiable contributor. Among seven modifiable risk factors assessed using a parametric piecewise constant hazards model with competing risk of death considered, smoking had the strongest and most statistically robust association with colon cancer incidence.

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What carcinoembryonic antigen level should trigger further investigation during colorectal cancer follow-up? A systematic review and secondary analysis of a randomised controlled trial

Authors: Agency for Healthcare Research and Quality, André, Boey, Carl, Cochrane, Duffy, European Parliament and Council, Freedman-Cass, Glasziou, Goldstein, Grossmann, Huang, International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use, Ito, Jeffery, Labianca, Laurence, Litvak, Locker, Minton, Moses, National Institute for Health and Care Excellence, Newton, Nicholson, Primrose, Reitsma, Robin, Sargent, Scheer, Shinkins, Shinkins, Staab, Sturgeon, Su, Takwoingi, Tan, Tsikitis, Verberne, Whiting

Published: January 1, 2017

A systematic review of 52 studies (9717 participants in aggregate; median study size 139, IQR 72–247) with secondary analysis of the FACS randomised controlled trial (582 patients from 39 NHS hospitals, 5-year follow-up) found that at the standard 5 µg/l CEA threshold, pooled sensitivity was 71% (95% CI 64%–76%) and specificity 88% (95% CI 84%–92%). In the FACS trial data, approximately 4 in 10 patients without recurrence experienced at least one false alarm, and 6 out of 10 positive tests were false alarms. Smokers were identified as particularly prone to multiple false-positive CEA results. The study concluded that continuing smokers should not be monitored with CEA testing at all, as smoking renders the surveillance tool unreliable for detecting treatable colorectal cancer recurrence.

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Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

Authors: A de la Chapelle, AM Moyer, AM Pittman, B D'Avanzo, C Chao, C Martínez, C Sachse, CR Sharpe, DM Gertig, DW Nebert, E Botteri, E Botteri, E Giovannucci, E Giovannucci, E Giovannucci, ED Paskett, EF Heineman, EM van der Logt, Guang Yin, H Bartsch, Hitoshi Ichimiya, Hoirun Nisa, IP Tomlinson, J Little, JA Agúndez, JA Agúndez, Jun Nagano, K Chen, K Huang, K Isomura, K Tajima, Kengo Toyomura, Kenji Takenaka, Kitaroh Futami, KM Smits, Koji Ikejiri, KT Kelsey, L Hou, L Sivaraman, M Arand, Masao Tanaka, ML Cote, ML Slattery, ML Slattery, N Ishibe, O Nyrén, P Lichtenstein, PD Terry, RC Strange, Reiji Terasaka, Ryuichi Mibu, S Kono, SC Cotton, Suminori Kono, T Hagiwara, T Katoh, T Oyama, Takafumi Maekawa, Takeshi Okamura, V Harth, Y Hoshiyama, Yohichi Yasunami, Yoshihiko Maehara, Yoshihiro Kakeji

Published: January 1, 2010

In this population-based case-control study of 685 colorectal cancer cases and 778 controls from the Fukuoka Colorectal Cancer Study, participants with ≥400 cigarette-years had a significantly elevated risk of rectal cancer (OR 1.60, 95% CI 1.04-2.45) compared to lifelong nonsmokers. Overall colorectal cancer risk showed ORs of 0.65 (95% CI 0.45-0.89) for <400 cigarette-years, 1.16 (95% CI 0.83-1.62) for 400-799 cigarette-years, and 1.14 (95% CI 0.73-1.77) for ≥800 cigarette-years. The increased risk at higher cumulative smoking exposure, particularly for rectal cancer, supports smoking avoidance as a preventive measure.

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Evaluation of Effective Factors in Incidence of Colorectal Cancer

Authors: دانشور, رضا, صابری, سید حسین, پورفرضی, فرهاد, یزدانبد, عباس

Published: December 11, 1391

In this case-control study of 80 colorectal cancer patients and 80 matched controls in Ardabil, Iran, a positive history of smoking increased the risk of colorectal cancer approximately 1.8 times (OR=1.78; 95% CI: 0.91-5.85). While the confidence interval crossed 1.0, the study conclusion listed smoking history as a contributing risk factor for colorectal cancer. No significant difference was observed between groups for alcoholic beverage consumption (p=0.385).

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