It’s a very enticing proposition….that a single, over the counter pill can reduce the risk of heart attack and stroke as well as cancer. Are we there yet? Should we be recommending routine aspirin use even in people without significant cardiovascular risk factors? (click here for a great review of the biology of aspirin by Dr. Quesnelle.)
Recent studies support this proposition although as with most studies, the devil is often in the details. Two meta-analyses led by Peter Rothwell of the University of Oxford examined the effects of aspirin on cancer incidence and death. The first analysis looked at patient data from 51 randomized trials that compared daily aspirin use with control treatments to prevent vascular events such as heart attacks and strokes. They found that aspirin use reduced the risk of non-vascular death by approximately 12% compared with a control treatment and this effect was mainly due to fewer cancer deaths after five years of aspirin usage.
A second analysis looked at whether aspirin use had any impact on the risk of metastasis from solid cancers. Once again, the patients were participants in five randomized trials comparing aspirin with control treatments to prevent vascular events. In total, 987 new solid cancers were diagnosed among the 17,285 participants. Patients who received aspirin were 46% less likely to have cancer with distant metastasis than those using a control treatment.
The researchers also evaluated the impact of aspirin on a specific type of cancer called adenocarcinoma, which can arise in many different organs. They learned that:
An article that just came out in the internationally influential medical journal Lancet that reviews the results from a series of trials that randomized patients to either a daily aspirin (any dose) vs. no aspirin (placebo or not) for at least a four year period. These studies were all done looking primarily for a difference in vascular/cardiovascular outcomes, but they also provide an opportunity to determine whether daily aspirin is associated with any other potential differences in medical outcomes.
There is certainly a background of research looking at the relationship between inflammation and cancer. There is also relatively recent evidence that daily aspirin reduces long-term risk of colon cancer, but this question hasn’t been addressed well with other cancers.
The trial took the results from over 25,000 patients in these eight randomized studies and found that there were very similar results from one to the next, so the results were pooled. The investigators only looked at rates of fatal cancers of various subtypes, with results obtained from records in death certificates and tumor registries.
There is a lot of information in these, but the clear take-home message was that the results became increasingly apparent with longer follow-up, particularly beyond 5 years and even more prominent in the period from 10 to 20 years out from starting vs. not starting daily aspirin. For a wide range of cancers, including gastrointestinal (GI) and non-GI, including lung, esophageal, and pancreatic cancers, and with trends for several other cancers as well, there was a significant decrease in the proportion of deaths from these cancers out to 20 years.