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Long term NSAIDs are associated with lower colorectal cancer risk, study shows

BMJ 2015; 351 doi: http://dx.doi.org/10.1136/bmj.h4599 (Published 25 August 2015) Cite this as: BMJ 2015;351:h4599
  1. Susan Mayor
  1. 1London

Taking low dose aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs) continuously in the long term is associated with a lower risk of colorectal cancer, a Danish case-control study has shown.1

The study, published in the Annals of Internal Medicine, analysed data on drug use, comorbid conditions, and history of colonoscopy from Danish prescription and patient registries. Researchers looked at the use of NSAIDs, including aspirin, in 10 280 people with a diagnosis of colorectal cancer in northern Denmark from 1994 to 2011 and compared this with 102 800 matched controls.

Results showed that taking low dose aspirin (75-150 mg) continuously for five years or longer was associated with a 27% lower risk of colorectal cancer (odds ratio 0.73 (95% confidence interval 0.54 to 0.99)). Non-continuous use of aspirin did not reduce colorectal cancer risk, said the study, which was funded by the Danish Cancer Society and Aarhus University Research Foundation.

Taking an NSAID other than aspirin was associated with an even greater reduction in colorectal cancer risk. This reduction was greatest in people who took NSAIDs with high cyclo-oxygenase-2 (COX 2) selectivity at a dose of at least one third (≥0.3) of the defined daily dose for at least five years. Their risk of colorectal cancer was found to be 43% lower than in people who were not taking regular NSAIDs (0.57 (0.44 to 0.74)).

“Long term, continuous use of low dose aspirin and long term use of non-aspirin NSAIDs was associated with a reduced risk for colorectal cancer,” said the researchers, led by Søren Friis, of the Danish Cancer Society Research Center in Copenhagen. They said that NSAIDs may reduce colorectal neoplasia by reducing prostaglandin production as a result of inhibiting cyclo-oxygenase enzymes.

But the study authors warned that only 2-3% of study participants taking low dose aspirin showed good adherence with long term, continuous use. “And these persons may have a risk profile for colorectal cancer that differs from that of the general population,” they added.

“The potential use of aspirin and non-aspirin NSAIDs is limited by the risk for gastrointestinal bleeding and, for most non-aspirin NSAIDs, cardiovascular risks,” the researchers noted. “These potential harms will need to be balanced against the chemopreventive benefits that our results indicate.”

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Cite this as: BMJ 2015;351:h4599

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