Does Aspirin Reduce the Risk of Cancer?

Does Aspirin Reduce the Risk of Cancer?

There are a growing number of studies evaluating the protective effect of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) on the development of various types of cancer. If you are someone fighting cancer and its reoccurence, then information about apirin and other NSAIDs helping to reduce the risk of cancer would be important to know, given how aspirin is inexpensive and readily available with few side effects. Yet the news is not consistent and this article will inform you by shedding light on the studies done on both sides.

Aspirin and NSAIDs are thought to influence cancer development through its effect on cyclooxygenase (COX) activity. Aspirin inhibits the COX enzymes, which convert arachidonic acid into prostaglandins, linked to inflammation. Aspirin as well as NSAIDs are believed to suppress tumor growth through its effect on apoptosis (programed cell death), cell migration, and angiogenesis (new blood vessel formation that cancer tumors rely on for growth). Also, aspirin has shown to have an anti-estrogen effect, that could be beneficial to certain types of breast cancer.

According to the National Cancer Institute, in 2020, an estimated 1,806,590 new cases of cancer will be diagnosed in the United States and 606,520 people will die from the disease.

The most common cancers (listed in descending order according to estimated new cases in 2020) are breast cancer, lung and bronchus cancer, prostate cancer, colon and rectum cancer, melanoma of the skin, bladder cancer, non-Hodgkin lymphoma, kidney and renal pelvis cancer, endometrial cancer, leukemia, pancreatic cancer, thyroid cancer, and liver cancer.

For men, the most common cancers diagnosed in 2020 are prostate, lung, and colorectal cancers that account for an estimated 43% of all cancers. For women, the three most common cancers are breast, lung, and colorectal, and they will account for an estimated 50% of all new cancer diagnoses in 2020.

There are many risk factors that contribute to the development of cancer including environmental, hereditary, lifestyle, and dietary habits. Cancer is sometimes referred to as the “perfect storm” because it is not usually caused by one thing and therefore not fully understood.

A study that followed 57,164 teachers linked aspirin use to a lower risk of breast cancer development. Through a follow up questionnaire that included their use of NSAIDs, it found that 3% of the women developed invasive breast cancer within eight years after an initial baseline health questionnaire. The study observed a reduced risk of breast cancer among participants who took three or more tablets of low-dose aspirin per week.

The results of the study found that developing breast cancer was associated inversely with taking three or more tablets of low-dose aspirin per week (23% of participants). It found a 16% lower risk of breast cancer among women regularly taking low-dose aspirin compared to those not taking NSAIDs and this was particularly evident in women with the hormone receptor-positive/HER2-negative subtype that showed a 20% reduction in risk. Interestingly, the use of three or more tablets of “other” NSAIDs was marginally associated with lower risk of breast cancer, and other associations with NSAIDs were generally null.

The study concluded that developing breast cancer was associated inversely with taking three or more tablets of low-dose aspirin per week (23% of participants). This is the first report to suggest that the reduction in risk occurs for low-dose aspirin and not for regular-dose aspirin and only among women with the hormone receptor-positive/HER2-negative subtype. This preliminary study builds on previous knowledge and further supports the need for formal cancer chemoprevention studies of low-dose aspirin.

Another study reported that long term use of aspirin inhibited breast cancer metastasis and decreased risk of breast cancer death among 4,164 nurses who had previously been diagnosed with breast cancer. The study concluded that among women living at least 1 year after a breast cancer diagnosis, aspirin use was associated with a decreased risk of distant recurrence and breast cancer death.

A prospective cohort study reviewed 13 previous studies that drew inconsistent results and examined the relationship between aspirin use and breast cancer risk across 857,831 participants.

According to the study, it confirmed a dose-response relationship between aspirin use and breast cancer risk. For clinical prevention, long term (>5 years) consistent use (2-7 times/week) of aspirin appears to be more effective in achieving a protective effect against breast cancer. It found a 14% lower risk after five years of taking aspirin and a even greater 46% reduction in risk after 20 years of aspirin use.

These studies do not examine how and why aspirin can reduce breast cancer risk, but according to an article by the BBC, doctors say that aspirin can dampen down chronic inflammation that over time can create an environment in which cancer thrives. By reducing inflammation, aspirin helps the immune system do its job in killing cancer cells. The article says that aspirin may help fight aggressive breast cancer by making hard-to-treat tumors more responsive to anti-cancer drugs. There is some evidence aspirin might help prevent certain other cancers and lower the risk of it spreading. But more research is needed before it can be recommended as treatment.

In Jane McLelland’s book, How to Starve Cancer… And Then Kill It with Ferroptosis she writes about how aspirin works to help fight cancer:

COX (cyclo-oxygenase) was an enzyme linked to inflammation. COX seemed to be involved in the process of helping to stimulate new blood vessel growth around the cancer, stimulating Vascular Endothelial Growth Factor (VEGF). These new blood vessels brought nutrients to the cancer to allow it to keep increasing in size, to fuel its growing biomass… Indeed, aspirin was a COX 2 inhibitor and a VEGF inhibitor.

Aspirin and dipyridamole, which are both antiplatelet drugs, synergistically serve to break down the platelet clumps and expose the abnormal macrophages to the rest of the immune system.

The National Cancer Institute has done research in published studies looking at aspirin’s protective effect against cancer, and there is consistent data that shows aspirin reduces the risk of colorectal cancer.


In the double-blind, randomized international CAPP2 trial, comprised of 861 patients with Lynch syndrome. Lynch syndrome is a hereditary condition associated with an increased risk of colorectal cancer and endometrial cancer, among other cancers. Patients were randomly assigned to receive high-dose 600 mg aspirin daily or placebo. Cancer outcomes were monitored for at least 10 years from recruitment.

The study reported it found significantly reduced overall risk of cancer for the aspirin group. It said the case for prevention of colorectal cancer with aspirin in Lynch syndrome is supported by the results.

There is evidence that also extends to individuals with average colorectal cancer risk as well. The National Cancer Institute says:

Among the most recent examples is an analysis of two large, long-running cohort studies published in June 2016 in JAMA Oncology. The study, led by Dr. Chan at Harvard, linked the use of aspirin for 6 years or longer with a 19% decreased risk of colorectal cancer and a 15% decreased risk of any type of gastrointestinal cancer.

Based on their analysis, the research team estimated that regular aspirin use could prevent nearly 11% of colorectal cancers diagnosed in the United States each year and 8% of gastrointestinal cancers…And several randomized clinical trials have shown that aspirin use “at any dose” can reduce the incidence of any polyps as well as advanced polyps, he said, both of which can be precursors to colorectal cancer.

The U.S. Preventive Services Task Force (USPSTF), created in 1984 and is independent of the United States government, had published guidelines in 2016 that generally supported the use of aspirin to prevent colorectal cancer. The USPSTF is currently commissioning an update.

The task force recommends initiating low-dose aspirin use for the primary prevention of cardiovascular disease (CVD) and colorectal cancer (CRC) in adults aged 50 to 59 who are willing to take low-dose aspirin daily for at least 10 years.

The USPSTF states that for adults younger than 50 years old and older than age 70, there is insufficient current evidence to assess the balance of benefits versus harms of initiating aspirin use for the primary prevention of CVD and CRC. The USPSTF concluded the decision to use aspirin for people aged 60–69 should be an individual one.

Findings that aspirin is beneficial in reducing the risk of other cancers have been mixed. Frontiers in Oncology published a study in the National Institute of Health, to assess the effect of aspirin use on the risk of colorectal, gastric, breast, prostate and lung cancer. A total of 88 cohort studies and seven randomized controlled trials (RCTs) were reviewed in the final analysis. The results revealed that regular aspirin use reduced the risk of colorectal cancer, gastric cancer, breast cancer, and prostate cancer, but it said it showed no association with lung cancer risk. Additionally, aspirin use had a protective effect on CRC risk. However, high frequency aspirin use was associated with increased lung cancer risk. It also concluded that high-dose aspirin use may increase prostate cancer risk.

Be sure to speak to your doctor first about starting a daily low-dose aspirin that may make sense for people at high risk for certain types of cancer. However aspirin is not for everyone because it comes with risks of gastrointestinal ulcers, bleeding, and allergic reactions. The risk may be too great to recommend an aspirin regimen among adults who drink alcohol, take anticoagulants drugs or have a history of ulcers. And aspirin is usually avoided in children and teens, due to the rare risk of Reye’s syndrome that can harm the brain, liver, and other organs.

The National Cancer Institute found limitations in many studies of aspirin and cancer risk, such as missing information about aspirin dose and duration of use. The other limitation is aspirin is often grouped with other NSAIDs, like ibuprofen, but they are different medicines and different chemicals that are not well studied. Should they be studied with cancer as a single class of drug, or should their effects on cancer be studied separately? Addressing these drawbacks may provide more consistent data.

There are many studies touting the benefits of aspirin as an anticancer agent, however there are mixed reports that need to be considered. Observational studies show promise that hint to aspirin’s anticancer effects across many different cancer types, and more research is needed. Additional studies are needed to show consistent data that aspirin can reduce the risk of cancers other than colorectal. Further investigation is helpful to find the minimum effective dose of aspirin required for cancer prevention. However, if aspirin’s anti-cancer effects are proven, then its potential lifesaving benefits may be even larger than previously recognized.

About The Author

Kendra Evans

Kendra Evans founded Inflammation Guide in April 2020. Our goal is keeping our readers informed to help them live an empowered and full life while they manage inflammation. Inflammation Guide provides a central location for breaking news and updates on prescriptions, treatments, supplements and alternative wellness solutions to give options to people living with at least one inflammatory condition.

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