The Lancet has published the results of a meta-analysis that aimed to assess the effect of aspirin in preventing death from cancer. The results of this study have been reported in the general media (BBC).
The review included data from 8 trials involving 25,570 individuals. The aspirin was used in each of these studies to prevent or treat atherosclerotic disease. These studies also collected data on cancer deaths. Individual patient data were available in 7 of the 8 studies.
The results from all 8 studies indicate a 21% relative risk reduction (pooled odds ratio [OR] 0·79, 95% CI 0·68–0·92, p=0·003) while the individual patient data analysis involving 7 studies indicated similar results over 5 years (hazard ratio 0·66, 0·50–0·87, p=0·003).
The data from all 8 studies shows an absolute risk of death from cancer of 3.01% in patient not taking aspirin compared to 2.33% in those assigned to aspirin. This is an absolute risk reduction of 0.68% or a number needed to treat (NNT) of 147 over approximately 5 years to prevent one death from cancer.
This analysis did not make any assessment of the harms of aspirin in this patient group.
Action: Clinicians should be aware of this study. The media reporting may generate patient queries. The chance of benefit is 6 or 7 in 1,000 over 5 years and perhaps more research needs to be done before recommending aspirin as a national cancer prevention strategy.