Aspirin and cancer prevention

Every month there seems to be a new study released about the potential for aspirin to reduce either cancer incidence or mortality. The latest came out this month in the Journal of the National Cancer Institute, authored by Eric Jacobs and colleagues from the American Cancer Society. Here is the full text (subscription or institutional access required, but if you don't have that you can always read the abstract), and even better here is a succinct summary from MedPage Today. The overall effect was relatively modest but seemed to show that daily users of aspirin had an 8% reduction in the risk of dying from cancer. The effect was more pronounced for the risk of dying from a cancer of the GI tract, since individuals using aspirin on a daily basis for 5 years or more had a 59% lower chance of dying of esophageal cancer and a 64% lower chance of dying of stomach cancer than those who did not take it.

The April 2012 issue of The Lancet also had two important papers relevant to this topic. One was an analysis of 51 randomized trials of aspirin use for another endpoint (vascular events), and it demonstrated that there was a 15% reduction in overall cancer deaths in daily aspirin users. The other  suggested that the effects could be seen more long term, since there was a reduction in the incidence of distant metastases, with a 36% reduction overall and even higher benefits seen in adenocarcinoma, particularly adeno's associated with GI primaries, including an amazing 74% reduction in the incidence of metastases from patients presenting with localized colon cancers. And the same may apply to the use of aspirin in women with Stage I-III breast cancer, based on a paper in the Journal of Clinical Oncology from 2010, which showed a protective effect especially in women surviving several years after initial diagnosis.

Speculating on the cause for these associations is beyond the scope of this blog post. Does this mean that we should be taking aspirin daily or at least several times weekly to ward off cancer? To my knowledge, no professional society or guideline is recommending the use of aspirin in this fashion just yet, and it is important to note that not all studies have shown a similar effect. Many of these studies were retrospective, which can lead to all sorts of biases and confounding factors, and can never truly prove cause and effect. And aspirin is not lacking in side effects, as serious bleeding was definitely associated with even a single baby aspirin a day. I am not yet routinely recommending the use of aspirin to my breast cancer patients who have completed treatment, since I am inherently skeptical about many of these things. But…the data are certainly provocative, and I am watching this story closely.