Can long-term aspirin use help prevent colorectal cancer?

Using aspirin for at least 6 years has been linked to “a modest but significantly reduced risk for overall cancer, especially gastrointestinal tract tumors,” according to a new study published in JAMA Oncology. The findings coincide not only with the National Colorectal Cancer Awareness Month, but also with the US Preventive Services Task Force (USPSTF) recommendation concerning the use of aspirin to prevent colorectal cancer (CRC) – reversing its position from 2007. The USPSTF does not endorse aspirin as direct method for the prevention of CRC – not to be confused with CCR – but does recognize a fringe benefit for people who are already benefitting from aspirin as a means of preventing cardiovascular events.

But can aspirin aspire to prevent cancer directly? According to an accompanying editorial, the new study brings us “one step closer” to that. Although “advancing the use of aspirin as a true cancer chemopreventive agent” would require further research – in particular to determine “an effective dose, the frequency and duration of treatment, and the clinical population at risk,” – “learning that aspirin’s preventive effects on GI tract cancer seem to extend even to those individuals who undergo CRC screening provides further support for aspirin’s possible future use as a cancer-preventive agent.” The authors are also point out that aspirin would be a complement – and substitute – of screening tests such as colonoscopy.

The researchers used data from two large cohort studies; the Nurses’ Health Study (1980-2010) and Health Professionals Follow-up Study (1986-2012). The two studies monitored a combined total of 135,965 healthcare professionals who reported on aspirin use every two years for over 32 years. Pretty much nothing happened during the first 5 years, but after that the scientists – led by Yin Cao, MPH, ScD – “observed a progressively greater reduction in the risk for gastrointestinal tract cancers.” In general, regular use of aspirin was linked to a 3% decreased risk for overall cancers, a 15% decreased risk for gastrointestinal tract cancers, and a 19% decreased risk for colon and rectum cancers. On the other hand, aspirin didn’t lower the risk for breast, prostate, lung, and other major cancers.

In spite of the somewhat modest results, the authors of the study estimate that regular use of aspirin could prevent nearly 30,000 GI tract tumors a year, as well as 7,4000 colorectal cancers in more than 41 million American adults between the ages of 50 and 75 who undergo screening – and a further 9,800 such cancers in the close to 30 million U.S. adults who do not undergo screening. Moreover, age; family history of cancer and cardiac risk factors; comorbid conditions, such as type 2 diabetes mellitus; reproductive factors; and other major lifestyle risk factors for cancer did not seem to affect the relative benefits of aspirin. “Regular aspirin use may prevent a substantial proportion of colorectal cancers and complement the benefits of screening,” the researchers wrote.

Related: Can aspirin reduce the risk of dying of prostate cancer?