LONDON – The daily, long-term use of low-dose aspirin cuts the risk of death from several types of cancer, in addition to colorectal cancer, according to data published online Dec. 6 in the Lancet.

Daily consumption of low-dose aspirin for 5 years or longer may cut the risk of death from several types of cancer.

In a meta-analysis of eight randomized clinical trials involving 25,570 patients, low-dose aspirin taken for 5 years or longer reduced mortality from esophageal, pancreatic, brain, stomach, colorectal, prostate, and even lung cancer, with doses as low as 75 mg/day having an effect.

This is the first time that low-dose aspirin has been linked to a reduction in cancer mortality other than colorectal cancer, said Dr. Peter M. Rothwell, who conceived and coordinated the research.

Dr. Rothwell of the John Radcliffe Hospital and the University of Oxford, U.K., and his associates in October 2010 showed that low-dose aspirin reduced the 20-year risk of new colon cancer cases by approximately one-quarter and deaths by a third (Lancet 2010;376:1741-50).

The current study looked at all deaths from cancer that occurred during or after completion of eight randomized clinical trials that had been performed to look at the effects of daily aspirin vs. control for the primary or secondary prevention of vascular events (Lancet 2010 [doi:10.1016/S0140-6736(10)62110-1]).

Across all eight trials, 674 cancer deaths occurred in 25,570 patients, with aspirin treatment significantly reducing the risk of death, compared with no aspirin treatment (pooled odds ratio [OR] 0.79, 95% confidence interval [CI] 0.68-0.92, P = .003).

Using individual patient data available for seven of the trials and in which 657 cancer deaths occurred in 23,535 patients, the benefit of aspirin therapy was apparent only after 5 years or more of follow-up. The hazard ratio (HR) for death from all types of cancer was 0.66 (95% CI 0.50-0.87, P =.003), with a greater effect seen in patients with gastrointestinal tumors (HR 0.46, 95% CI 0.27-0.77, P =.003).

"We found that within the trials, while people were still on aspirin vs. no aspirin, the aspirin group had about a 30%-40% reduction in cancer deaths between year 5 and the end of the trial," Dr. Rothwell said at a press briefing.

To determine the longer-term effects of aspirin on cancer mortality, the team looked more closely at data from three of the trials. These had all been conducted in the United Kingdom and continued to collect information on cancer deaths via national death certification and cancer registration systems long after the trials had concluded.

In all, individual patient data were obtained on 1,634 cancer deaths that had occurred in 12,659 patients. Aspirin was found to reduce the 20-year risk of death from all solid cancers by 20% (HR 0.80, 95% CI 0.72-0.88, P less than .0001). Again, the effect on gastrointestinal cancer was greater (HR 0.65, 95% CI 0.54-0.78, P less than .0001), but there was no effect on hematologic malignancies.

At least 5 years of therapy were needed to reduce the risk of death from esophageal, pancreatic, brain, or lung cancer, with 10 years or more treatment required to see any effect on stomach and colorectal cancer death rates, and 15 years or more for prostate cancer. With regard to both lung and esophageal cancer, the effect of aspirin was limited to adenocarcinomas.

While the findings do not mean that everyone over the age of 40 years should now suddenly start taking a daily dose of aspirin to prevent cancer, given the increased risk of bleeding in some individuals, "We should probably stop taking people off aspirin unless they’ve got side effects," Dr. Rothwell said in an interview, adding "We probably shouldn’t discourage those who want to take aspirin as actively as we have been doing," and perhaps physicians should "think about prescribing aspirin more in people at increased vascular risk, because they certainly benefit already."

"There is a fundamental difference between the treatment and the prevention of a disease," said Dr. Peter Elwood, professor of epidemiology at Cardiff University, Wales.

Dr. Elwood suggested that deciding to take a daily dose of aspirin to prevent cancer could be another choice patients make once they have all the relevant facts, much as lifestyle changes are advised but not prescribed for cardiovascular disease prevention.

The study was conducted independently of commercial interests. Dr. Rothwell has received honoraria from pharmaceutical companies with an interest in antiplatelet therapy, including AstraZeneca, Bayer, Boehringer Ingelheim, Sanofi-Aventis/BMS, and Servier. Dr. Elwood reported no relevant financial disclosures.

Low-Dose Aspirin Cuts Cancer Death Rate by 30%-40%