Lancet also had 2 articles on aspirin and cancer (both from same group in UK). This is the same impressive group that did a whole lancet issue a few years ago on blood pressure variability and stroke (in a previous post on hypertension).
1. looked at 5 trials using aspirin, at least 75mg/d, to decrease vasc events, with 6.5 yrs followup. Many old studies suggested dec in colon ca with asa or nsaids, most with positive results. This study of 17K pts found 36% dec risk of distant mets overall in pts with cancer, with the vast majority of effect in adenoca — 48% dec risk of metastases in those with adenoca. Esp effective in those without mets at diagnosis (50% decrease). Essentially all of the graphs show continuing divergence of curves for the first approx 8 years, then plateauing, for lung, bone, brain, and other mets. The total number of cancers detected and elligible for analysis was 775. (they do not give absolute risk reductions, but to my simplistic analysis, about 5% of pts had cancer, about 50% reduction, so on the order of 2.5% of population with benefit).
Those on lower dose aspirin did the best. For the most common adenocarcinomas (esp those without mets already), the results were consistent (colorectal 73% reduction, breast 84% reduction, prostate 66% reduction). Pretty impressive. See doi: 10.1016/S0140-6736(12)60209-8.
2. study on cancer incidence in pts taking daily aspirin, short-term effects. In 34 trials of 69K pts, 15% dec cancer deaths, esp after 5 yrs. In primary prevention trials of low dose asa (6 trials, 36K pts), after 3 years cancer incidence dec 24%. Initially the benefit of asa was offset by inc bleeding, but that outcome diminished after 3 years, with continuing benefit in cancer incidence. For some reason (??) case-fatality rate from major extracranial bleeds lower on asa, though there was twice the risk of extracranial bleeds in the 1st 3 yrs, no increased risk afterwards.(intracranial bleeds included in “major vascular events” category). Curves on cancer incidence ess the same for first 4 years, then diverge and stay diverged, demonstrating consistent benefit from aspirin. Subgroup analyses (men/women, age more or less than 60, smoker) all show the same, with no real effect for 1st 3 years, but after 3 years there is a consistent absolute reduction of 3 cancers/1000-patient years. See doi: 10.1016/S0140-6736(11)61720-0.
Geoff
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