All too often, we hear or read in the media that eating a certain food, taking a supplement, or changing a behavior will stave off cancer or heart disease, or it will help us lose weight. But it is important that we not take scientific publications for more than they claim to be.
In the August edition of the Journal of Clinical Oncology, Choe et al present a compelling study showing an association between aspirin use and decreased mortality from prostate cancer.
The coagulation pathway, which is responsible for the clotting of blood, has been known to play a role in the spread of cancer cells. The question has been raised in the past that if cancer cells depend on the coagulation pathway in part to spread, will blocking a portion of that pathway help prevent the spread of cancer?
In their publication, the authors evaluated 5,955 patients enrolled in a large prostate cancer specific database (CaPSURE data). The patients had been treated for prostate cancer that had not spread beyond the prostate gland with either surgery to remove the prostate, or radiation to the gland. Data was collected over a 70 month period.
The results showed that patients who took anticoagulants of any kind had a lower risk of prostate cancer death and patients who took aspirin as part of their regimen had an even lower risk of death from prostate cancer.
While the authors have presented very important data, they are very clear that their conclusions do not support changing current therapy for prostate cancer patients.
The study they presented is observational in nature; that is, they are looking at a group of patients who took certain medications and saw a correlation between such medications, and patient outcomes (taking aspirin was associated with a lower risk of prostate cancer-specific death). They very clearly stop short of making the case for a causative relationship (e.g. aspirin prevents prostate cancer death) between anticoagulants and the risk of prostate cancer death.
The reason for this lack of certainty is rooted in the fact that observational studies are subject to confounding factors that can affect study outcomes. In this case, the authors note that patients who took anticoagulants may have had other medical problems that led to their demise before their prostate cancer could have had a chance to spread. This would have the appearance of lowering prostate cancer deaths.
The authors point out the best way to answer the question of whether anticoagulants (or aspirin in particular) prevent prostate cancer death is to design a forward looking study to start patients randomly on aspirin or placebo and evaluate the two groups for differences in the occurrence of prostate cancer-specific death.
This blog post was contributed by Keith D. Bloom, M.D., a urologist on the medical staff at Baylor Medical Center at Irving.