Cancer Prevention: Another Potential Benefit of Low-Dose Aspirin

Cancer killed close to 590,000 Americans in 2014, accounting for 1 in 4 deaths. This inexpensive medication also shows promise to prevent certain cancers.

Mechanisms Proposed for the Action of Aspirin in Cancer Prevention

Blocking Inflammation

Inflammation is a normal response to tissue injury or infection that helps clear infection or helps heal injured tissue. Over time, however, chronic inflammation can cause DNA mutations and promote tumor development and growth. Aspirin reduces chronic inflammation and the production of inflammatory proteins (prostaglandins) that may promote cancer.15

Inhibiting Platelet Function

Platelets can promote cancer spread by shielding cancer cells from the immune system. Aspirin may interfere with platelets’ shielding effect and make cancer cells less likely to metastasize.

Cancer Prevention

Cancer cases are expected to increase by 57% worldwide in the next 20 years.10

  • Half of all cancers are preventable and could be avoided by fully implementing current guideline-based recommendations
  • Simple strategies for lowering the risk of heart disease also help prevent many types of cancer.
  • New efforts are required to put this knowledge into practice.

Aspirin and Cancer

  • The benefits of aspirin in secondary prevention of heart attacks are well documented. Individuals at high risk for a first heart attack or stroke benefit as well. New evidence suggests that aspirin is also useful in cancer prevention.1,3
  • While the evidence for aspirin is strongest for prevention of colorectal cancer, the benefits of aspirin appear to apply to other types of cancer.
  • Scientific data to support cancer prevention by aspirin come from:
    • Clinical trials of aspirin originally conducted to study heart disease and stroke prevention, including long-term follow-up after trial completion.
    • Clinical trials of aspirin in pre-cancerous conditions, such as polyps in the colon.
    • Clinical trials of aspirin in patients with familial cancer syndromes, such as Lynch syndrome.
    • Long-term observational studies of aspirin use in populations.
    • Case-control studies of specific cancer types.1,3

Any decision to recommend aspirin to patients must balance the potential harms of aspirin again aspirin’s potential benefits. Aspirin should not be recommended for individuals at low risk of MI, CVA and colorectal, melanoma, ovarian, breast and prostate cancers.

Aspirin and Cancer Prevention: What’s the Evidence?

  • Data from several clinical trials whose primary endpoints were vascular events, shows that aspirin taken daily for 4 or more years was associated with an 18% reduction in overall cancer deaths.1
  • This risk reduction was due mainly to fewer cancer deaths among participants who took aspirin for at least 5 years.1
  • Long-term follow-up of a large aspirin clinical trial showed a 20% reduction in risk of colorectal cancer over extended follow-up.3
  • Long-term follow-up of patients with a hereditary cancer syndrome (Lynch) showed a 30-40% reduction in risk of new cancers over extended follow-up.6,14,15
  • Long-term daily aspirin use, ≥325 mg/day for≥5 years, is associated with reduced incidence of colorectal cancer compared with non- users.1
  • Clinical trials using 75–325 mg per day of aspirin for 3 years reduced the risk of recurrence of precancerous colorectal polyps by 17%.6,7
  • The use of aspirin for 5 years or longer reduced the incidence and mortality of colorectal cancer by 30%–40% after 20 years of follow-up.15
  • Use of a daily low dose aspirin lowers the risk of ovarian cancer by about 20%.8
  • A 2014 study found that women who took aspirin on a regular basis reduced their risk of developing melanoma by 21%.9

Mounting evidence supports the use of aspirin for the primary prevention of certain cancers. Aspirin prescription should be based on careful evaluation of individual risk factors and potential harms from bleeding.

Aspirin Prescribing: How to Decide

  • Universal use of aspirin is not recommended even in high-risk populations.
  • Aspirin has potential harms, especially the risk of bleeding.
  • The decision to prescribe aspirin should be individualized.
  • Before prescribing aspirin, consider the balance of potential benefits vs. potential harms and discuss this with your patient.

Aspirin Harms

  • Excessive bleeding is the greatest potential harm from aspirin, including gastrointestinal bleeding and hemorrhagic stroke.1,10
  • These harms increase with age and are greater for men than women.10
  • Harms are more strongly related to dose than duration of aspirin use.4
  • In women and men without risk factors for gastrointestinal bleeding, the rate of excess serious bleeding associated with aspirin is shown in this table:2
Age in Years Bleeding Events per 1,000 Person-Years, Women Bleeding Events per 1,000 Person-Years, Men
60 to 69 1.2 2.4
70 to 79 1.8 3.6
Over 79 3.0 6.0

Aspirin Benefits

Aspirin reduces some cancers by 18% overall.3,8,11 Aspirin may be especially effective in preventing:

  • Colorectal Cancer
  • Prostate Cancer
  • Breast Cancer
  • Melanoma
  • Ovarian Cancer

Aspirin Dose and Other Factors Affecting the Impact of Aspirin on Cancer Prevention and Survival

  • Factors that affect aspirin’s impact on cancer include population characteristics, aspirin dose and duration of use.1,2
  • Most studies have not seen a sizable difference in the benefits from aspirin between low-dose aspirin (e.g., 81 mg) and higher doses.1
  • Certain genetic and lifestyle factors impact the extent to which aspirin can reduce cancer risk or cancer progression, but these factors are still under investigation.15
  • In addition to the population characteristics, certain cancer subtypes may show greater potential benefit from aspirin. For example, in colorectal cancer patients, aspirin treatment was particularly effective in patients with overexpression of tumor COX-2 (an enzyme that triggers inflammation).13
  • The benefits of aspirin in cancer prevention increase with duration of use.
Talk with your patients about aspirin therapy for both cardiovascular disease and cancer prevention.

Cancer Sites Affected by Aspirin

  • Women
    • Breast
    • Colon and rectum
    • Ovary
    • Skin (melanoma)
  • Men
    • Breast
    • Colon and rectum
    • Prostate
    • Skin (melanoma)

A Practical Approach

  • Aspirin should be considered for those at high risk of colorectal cancer.
  • 2016 U.S. Preventive Services Task Force (USPSTF) recommendations on aspirin use include colon cancer prevention in the rationale for aspirin use.
  • It may be appropriate to consider aspirin’s cancer prevention benefits, particularly in patients who are:
    • At risk for colorectal cancer.
    • At moderate to high risk for a first heart attack and stroke who are not already taking aspirin.
    • At moderate-high risk for a first heart attack or stroke who are not already taking aspirin.
    • Determine your 10-year risk of heart disease or stroke with this American Heart Association Heart Risk Calculator


Cancer Prevention: Another Potential Benefit of Low-Dose Aspirin (4-page PDF)


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Posted on: January 29, 2018

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