FPIN's Clinical Inquiries

Aspirin for Colon Cancer Risk Prevention


Am Fam Physician. 2019 Nov 1;100(9):online.

Clinical Question

What is the role of aspirin in colon cancer risk prevention?

Evidence-Based Answer

Daily low-dose aspirin can be offered to patients older than 50 years for colon cancer prevention. (Strength of Recommendation: B, based on multiple meta-analyses but undermined by one large randomized controlled trial [RCT].) When aspirin is taken daily for at least 10 years, it decreases mortality risk from colorectal cancer (CRC; number needed to treat [NNT] = 1,500 person-years), decreases the risk of metastasis in patients with localized adenocarcinoma, and decreases CRC stage at diagnosis. One large primary prevention RCT of women taking alternate-day low-dose aspirin showed no difference in CRC prevalence or death.


A 2011 meta-analysis of eight RCTs with 25,570 participants studied the effects of aspirin on cardiovascular disease (CVD) prevention.1 Trials were included if they compared patients taking any dose of daily aspirin with those not taking aspirin, with or without another antiplatelet or antithrombotic medication. The authors performed a post-hoc analysis of the trials lasting more than five years (three trials; n = 12,915) and found a 50% reduction in CRC mortality in patients taking aspirin after follow-up of at least 10 years. No benefit was seen before 10 years. In addition to comparing low-dose aspirin with placebo, one of the RCTs compared warfarin with placebo and found no effect on CRC mortality.

A 2012 meta-analysis of five RCTs with 17,285 participants studied the effect of daily low-dose aspirin on metastasis over 6.5 years.2 Inclusion criteria were the same as in the 2011 meta-analysis. Of the patients with solid cancer in whom metastasis status was known, 130 cases of CRC were analyzed. The risk of metastasis in those taking low-dose aspirin was lower than in the control group (37% vs. 61%; odds ratio = 0.36). The study also showed a decreased 10-year risk of metastasis in patients with localized CRC (hazard ratio = 0.26). In patients with

Address correspondence to M. Shoaib Khan, MD, at mshoaibkhan@hotmail.com. Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Rothwell PM, Fowkes FG, Belch JF, et al. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Lancet. 2011;377(9759):31–41....

2. Rothwell PM, Wilson M, Price JF, et al. Effect of daily aspirin on risk of cancer metastasis: a study of incident cancers during randomised controlled trials. Lancet. 2012;379(9826):1591–1601.

3. Cook NR, Lee IM, Gaziano JM, et al. Low-dose aspirin in the primary prevention of cancer: the Women's Health Study: a randomized controlled trial. JAMA. 2005;294(1):47–55.

4. Chubak J, Kamineni A, Buist DS, et al. Aspirin use for the prevention of colorectal cancer: an updated systematic evidence review for the U.S. Preventive Services Task Force. Evidence synthesis no. 133. AHRQ publication no. 15-05228-EF-1. Agency for Healthcare Research and Quality; 2015.

5. Bibbins-Domingo K. Aspirin use for the primary prevention of cardiovascular disease and colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2016;164(12):836–845.

Clinical Inquiries provides answers to questions submitted by practicing family physicians to the Family Physicians Inquiries Network (FPIN). Members of the network select questions based on their relevance to family medicine. Answers are drawn from an approved set of evidence-based resources and undergo peer review. The strength of recommendations and the level of evidence for individual studies are rated using criteria developed by the Evidence-Based Medicine Working Group (https://www.cebm.net).

The complete database of evidence-based questions and answers is copyrighted by FPIN. If interested in submitting questions or writing answers for this series, go to https://www.fpin.org or email: questions@fpin.org.

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of FPIN's Clinical Inquiries published in AFP is available at https://www.aafp.org/afp/fpin.



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