Evidence growing that aspirin helps prevent cancer

Taken from The Lancet – by Bruce Sylvester – Two papers published in March, 2012 in The Lancet suggest that daily aspirin use can be protective against cancer.

The studies were undertaken by Professor Peter M Rothwell, University of Oxford (UK), John Radcliffe Hospital, Oxford, and colleagues.

In the first  paper, the investigators evaluated individual patient data from 51 randomized trials of daily aspirin versus no aspirin for the prevention of vascular events such as heart attacks.

Aspirin reduced the risk of a cancer death by 15% compared with controls. The aspirin benefit changed to a 37% reduced risk of a cancer death for those using daily  aspirin for 5 years or more.

The reduction in cancer deaths on aspirin translated to a 2% reduction in non-vascular deaths overall. during the trials, and the reduction in non-vascular deaths accounted for 91% of prevented deaths.

Daily low-dose aspirin reduced cancer incidence by about a quarter for use of 3 years-plus, with similar reductions in men (23%) and women (25%).

The investigators wrote, “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.”

In the second Lancet study, the authors collected new data on metastases of cancers that were diagnosed during all five large randomized trials of daily aspirin (75mg or more daily) versus control for the prevention of vascular events in the UK.

They reported that, with a mean follow-up of 6.5 years, aspirin use reduced risk of cancer with distant metastasis by 36%, risk of adencarcioma by 46%, and of other solid cancers by 18%, due mainly to a reduction by almost half in the proportion of adenocarcinomas with metastatic disease.

They also reported that aspirin reduced the risk of adenocarcinoma with metastasis at initial diagnosis by 31%, and risk of metastasis on subsequent follow-up in patients without metastasis initially by 55%, notably in patients with colorectal cancer(74%), and in patients on drug trial treatment up to or after diagnosis (69%).

Aspirin reduced by about half death due to cancer in patients who developed adenocarcinoma,  especially those without metastasis at diagnosis. Aspirin reduced by 35% the overall risk of fatal adenocarcinoma in the trial populations, but not the risk of other fatal cancers (such as blood cancers).

The effects of aspirin were independent of age, and sex.

“These findings provide the first proof in man that aspirin prevents distant cancer metastasis. Previous animal studies had shown that platelets play a part in metastasis of cancer via the bloodstream to distant tissues and that such metastasis might be prevented by aspirin,” said the authors.

“That aspirin prevents metastasis at least partly accounts for the reduced cancer mortality recently reported in trials of aspirin versus control in prevention of vascular events and suggests that aspirin will also be effective in treatment of some cancers. The lack of dependence of this effect of aspirin on its systemic bioavailability suggests that it is platelet-mediated. Other antiplatelet drugs might therefore have a similar effect on risk of metastasis and combining different drugs might increase benefit,” they added.