Taking a low dose of aspirin every day reduces the long term risk of several cancers and the risk of distant metastasis, suggests new evidence published in The Lancet.

A new analysis of data from 51 trials involving more than 77,000 patients, suggests that the protective effect of aspirin occurs within three to five years - much sooner than the 10 years that previous studies had suggested.

Prof Peter Rothwell and colleagues from Oxford University also showed that regular use of aspirin was associated with a reduced proportion of cancers with distant metastasis.

The trials were designed to compare aspirin with no treatment for the prevention of heart disease, however analysis of the results has shown the effect of taking regular aspirin and cancer incidence.  Regular aspirin use was associated with a reduced risk of colorectcal cancer as well as oesophageal, gastric, biliary and breast cancer.

Taking a low (75-300mg) daily dose of the drug cut the total number of cancer cases after only three years - there were nine cancer cases per 1,000 each year in the aspirin-taking group, compared with 12 per 1,000 for those taking placebo pills.

Aspirin also reduced the risk of a cancer death by 15% within five years, if patients stayed on aspirin for longer their risk appeared to go down even further - by 37% after five years.

Low-dose aspirin also appeared to reduce the likelihood that cancers, particularly bowel, would metastasise to other parts of the body. The researchers estimated that for every five patients treated with aspirin one metastatic cancer would be prevented.

However taking doses of aspirin does increase the risk of a major bleed, especially in the first few years of taking the drug. People are advised to discuss taking aspirin with a health care professional. 

Related articles: Aspirin for the older person: report of a meeting at the Royal Society of Medicine, London, 3rd November 2011

Conference Coverage: Aspirin Foundation 2011

Refernces


Rothwell PR, et al "Short-term effects of daily aspirin on cancer incidence, mortalilty, and nonvascular death: Analysis of the time course of risks and benefits in 51 randomized controlled trials" Lancet. 2012; DOI:10.1016/S01450-6736(11)61720-0.


Rothwell PM, et al "Effect of daily aspirin on risk of cancer metastasis: A study of incident cancers during randomized controlled trials" Lancet 2012; DOI:10.1016/S0140-6736(12)60209-8.


Rothwell PM, et al "Effects of regular aspirin on long-term cancer incidence and metastasis: A systematic comparison of evidence from observational studies versus randomized trials." Lancet Oncol 2012; DOI:10.1016/S1470-2045(12)70112-2.

BBC News, Daily aspirin 'prevents and possibly treats cancer'