A Little Aspirin Can Go a Long Way in Preventing Colon Cancer

New research shows that a lower dose of aspirin can provide the benefits of preventing certain cancers, without the adverse effects.

Aspirin taken at a low dose was shown to lower the risk of colon cancer and reduce mortality, according to findings published in The Lancet, which also demonstrate the drug’s benefit in preventing cancers that are difficult to detect.

In the study, Peter Rothwell, MD, of John Radcliffe Hospital in Oxford and colleagues evaluated the effects of low-dose aspirin (75-300mg daily) on incidence and mortality due to colorectal cancer in relation to dose, duration of treatment, and site of tumor. Previous research has demonstrated that high-dose aspirin (≥500mg daily) can reduce the long-term incidence of colorectal cancer; however, its potential is limited by a number of adverse effects, including bleeding in the stomach and intestines.

To determine whether a lower dose can provide the benefits of aspirin without the risks, the authors examined data from four randomized trials of aspirin versus control in the primary (Thrombosis Prevention Trial, British Doctors Aspirin Trial) and secondary (Swedish Aspirin Low Dose Trial, UK-TIA Aspirin Trial) prevention of vascular events and one trial of different doses of aspirin (Dutch TIA Aspirin Trial), and established the effect of aspirin on the risk of colorectal cancer over 20 years during and after the trials by analysis of pooled individual patient data.

In the four trials of aspirin versus control, 391 (2.8%) of 14,033 patients had colorectal cancer during a period of 18 years, and use of aspirin was shown to reduce the 20-year risk of colon cancer, but not rectal cancer. Taking aspirin lowered the risk of cancer of the proximal colon, but not the distal colon, they found. However, the benefit increased with scheduled duration of treatment, with use of aspirin for five years or longer lowering the risk of proximal colon cancer by about 70%.

Conversely, there was no added benefit at doses of aspirin greater than 75mg daily, with an absolute reduction of 1.8% in 20-year risk of any fatal colorectal cancer after 5-years scheduled treatment with 75-300mg daily, said the authors. However, the risk of fatal colorectal cancer was higher on 30mg versus 283mg daily on long-term follow-up of the Dutch TIA trial.

Low-dose aspirin taken for several years, they concluded, “reduced long-term incidence and mortality due to colorectal cancer,” adding that the “benefit was greatest for cancers of the proximal colon, which are not otherwise prevented effectively by screening with sigmoidoscopy or colonoscopy.”

In a commentary published in The Lancet, Robert Benamouzig, MD, and Bernard Uzzan, MD, of Avicenne Hospital in Bobigny, France, wrote that the study should “incite clinicians to turn to primary prevention of colorectal cancer by aspirin at least in high risk-populations. Specific guidelines for aspirin chemoprevention would be the next logical step.”

To access the study, click here.

Do you recommend low-dose aspirin to your patients who are at risk of developing colon cancer, or do you still believe that the risks outweigh the benefits?