Taking aspirin on a daily basis to reduce cancer risk should only be done under medical advice, according to the Irish Cancer Society.
The society was commenting on three new studies published by The Lancet journal that add to mounting evidence of the drug’s anti-cancer effects.
The studies, involving 200,000 patients, show the drug prevents development of cancers and reduces the spread of the disease from one organ to another.
It appears the longer aspirin has been taken, the greater the degree of protection.
One study showed that taking aspirin daily reduced the risk of developing cancer by about a quarter after three years. After five years, the risk of dying from cancer was reduced by 37%.
The second study focused on aspirin’s impact on cancer spread. Metastasis data were collected from patients diagnosed with cancer while taking part in five large, randomised heart attack and stroke prevention trials.
Over an average period of 6.5 years, taking low-dose aspirin every day was found to reduce the overall risk of distant-spreading cancer by 36%. For common solid cancers, including bowel, lung and prostate, the risk was reduced by 46% and for bladder, kidney and other solid cancers by 18%.
Aspirin reduced the proportion of cancers that spread instead of staying localised by 48%.
Many people take a 75mg dose of aspirin each day to guard against heart attacks and strokes.
“If one is considering starting to take aspirin, this should only be done under medical advice,” said Professor John Fitzpatrick, head of research at the ICS.
“For example, there is no indication as to what the optimal age is at which to start taking aspirin.”
Many people already take daily aspirin as a blood thinner to prevent stroke, but there is an increased risk of internal bleeding, particularly in the stomach.
The study’s lead res-earcher, Prof Peter Rothwell from Oxford University, said it was time to add prevention of cancer to the analysis on the balance of risk and benefits of aspirin.
He said there was an urgent need for clinical trials of treatment regimes incorporating aspirin.
Two US experts commenting in The Lancet pointed out some limitations to the research. Dr Andrew Chan and Dr Nancy Cook, from Harvard Medical School in Boston, said the analysis did not include findings from two large US trials that failed to show an anti-cancer benefit from taking aspirin every other day.
The researchers may also have missed the effect of pre-cancerous cells being removed from patients either through screening or the effects of aspirin-associated bleeding, they added. Some analyses were also limited by the quality of available data.
However the US experts concluded: “These caveats notwithstanding, Rothwell and colleagues show quite convincingly that aspirin seems to reduce cancer incidence and death.”
© Irish Examiner Ltd. All rights reserved