Evidence Mounts for Aspirin's Anticancer Attributes



Adults who take aspirin daily have a 15% reduced risk of death from cancer compared with controls, and a 37% reduced risk of cancer death after 5 years, based on data from 51 randomized trials of daily aspirin use vs. no aspirin.

The findings were published online in the Lancet on March 20.

Findings from previous studies have suggested a cancer-prevention role for aspirin, but long-term data were limited and incomplete, said Dr. Peter Rothwell of the University of Oxford (England), and his colleagues.

The researchers reviewed data from the Antithrombotic Trialists’ Collaboration, PubMed, and Embase. They included only trials of daily aspirin vs. no aspirin.

Overall, randomization to aspirin significantly reduced the risk of nonvascular death in patients in the 51 trials compared with no aspirin (1,021 vs. 1,173, respectively, P = .003).

In a review of cancer deaths from 34 of the 51 studies, aspirin was associated with significantly fewer cancer deaths, compared with controls (562 vs. 664, P = .008). The benefit was most evident in patients in trials lasting 5 years or longer, the researchers said (Lancet 2012 March 20 [doi: 10.1016/S0140-6736(11)61720-0]).

In terms of primary prevention, daily aspirin use significantly reduced the risk of a composite outcome of major vascular events, cancer, or fatal extracranial bleeds (P = .0002), the researchers noted.

The findings were limited by the focus only on daily aspirin use, and by the use of composite outcomes, the researchers said. However, the results suggest that aspirin reduces cancer incidence and mortality, they noted.

"In view of the very low rates of vascular events in recent and ongoing trials of aspirin in primary prevention, prevention of cancer could become the main justification for aspirin use in this setting, although more research is required to identify which individuals are likely to benefit most," they said.

The study should be considered in the context of two additional studies by Dr. Rothwell and his colleagues, one published online in the Lancet, and the other published online in the Lancet Oncology, the researchers added.

In the additional Lancet study, a review of five large, randomized trials of daily aspirin of at least 75 mg versus controls, daily aspirin significantly reduced the risk of cancer metastases by 30%-40% in the short term.

These findings may explain the early reduction in cancer risk associated with aspirin that was observed in the primary prevention trials, and the results "are likely to underestimate the true effects of aspirin," they noted (Lancet 2012 March 20 [doi: 10.1016/S0140-6736(12)60209-8]).

In the Lancet Oncology, a review of case-control studies, cohort studies, and randomized trials of aspirin use showed significant reductions in the risk of colorectal cancer, as well as significant reductions in the risk of esophageal, gastric, biliary, and breast cancer. The greatest impact was on the reduction in risk of gastrointestinal cancers (Lancet Oncol. 2012 March 20 [doi: 10.1016/S1470-2045(12)70112-2]).

Both of these additional studies support the role of aspirin in reducing cancer deaths.

The studies were independent of company funding. Dr. Rothwell has received honoraria for talks, advisory board participation, and clinical trial committee participation from multiple companies, including AstraZeneca, Bayer, Boehringer Ingelheim, Sanofi-Aventis/Bristol-Myers Squibb, and Servier, and is on the executive committee of the ARRIVE trial.

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