Aspirin reduces risk of prostate cancer mortality
October 20, 2012
Jacob Schor, ND, FABNO
A new paper on aspirin and prostate cancer has me again reassessing what I think about this medication. As a naturopathic doctor I am supposed to favor natural substances for treating disease and avoid pharmaceutical agents. Yet aspirin is one of those things that kind of straddles the line between natural agent and pharmaceutical drug. But let’s come back to this in a few moments. First let me summarize the recent study.
Published October 1, 2012 in the Journal of Clinical Oncology, this study analyzed the association between anticoagulant use and cancer outcome in men who had been previously treated for prostate cancer.
The researchers used data from participants in the “Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) Study,” a observational registry of men who have been diagnosed prostate cancer starting in 1995. Patients from 41 institutions nationwide have been enrolled in this study. Data from 5,955 men, who were treated with either radiation therapy or radical prostatectomy, were analyzed. These men were followed for about 6 years, at which point 779 patients had died and of these 193 (25%) had died of prostate cancer.
Of these nearly 6,000 men, 2,175 (37%) had taken some type of anticoagulant therapy, the majority (84%) had taken aspirin and about a fifth (21%) warfarin. Some obviously had taken both.
The researchers looked at he risk of dying from prostate cancer-and compared it between those men on anti-coagulant therapy and those not.
Those men taking anticoagulants had a significantly lower risk of dying from prostate cancer. At 7 years only 1 % of those taking anticoagulants had died compared to 3% of those not taking anticoagulants. At ten years these number had grown to 3% and 8%. Those taking anticoagulants also had significantly lower risk of disease recurrence and bone metastasis.
The impact of anticoagulant use was more pronounced in those with high-risk disease. In this subgroup, risk was 4% for those taking anticoagulants died of prostate cancer compared to 19% for those not taking anticoagulants.
The data was further analyzed in a Cox proportional hazards regression model comparing aspirin use, other anticoagulant use, initial PSA, treatment modality and Gleason score. This confirmed that aspirin use was independently associated with lower a 57% lower risk of dying of prostate cancer. Use of other non-aspirin anticoagulants did not change risk significantly.
These are convincing numbers, the sort of numbers that should convince a man, who has been diagnosed and treated for high-risk prostate cancer, to take aspirin Taking baby aspirin may increase his chance of surviving for ten years by a factor of nearly five. For your average guy who has had prostate cancer, taking aspirin will reduce his risk of dying from the cancer by more than half.
That should get your attention.
There is still no consensus as to why or how aspirin has an effect on cancer. Scientists had thought the effect resulted from aspirin blocking COX-2 activity. Blocking COX-2 blocks the inflammation that aids tissue recovery from injury, this inflammation also appears to aid and encourage tumor cell growth. A second hypothesis suggests that aspirin blocks production of NF-kappaB. Both explanations suffer a similar weakness. The doses of aspirin now shown to protect from cancer are so low that they are not adequate to impact either COX-2 or NF-kappaB.
A third possible explanation, favored in the current paper, is that aspirin affects platelets. Even low dose aspirin impairs platelet activity. In metastasis, as cancer cells spread through the blood, they are typically surrounded by platelets, which may somehow aid them in colonizing new sites for growth. It may be that because it decreases and impairs platelets, is the reason why aspirin acts against cancer. This argument is supported by the lack of anti-cancer action seen with the other anti-coagulants tracked in this study that do not impede platelet activity.
It is not a lack of understanding the mechanism of action that hinders aspirin use by my colleagues and our patients. It is often more a matter of principle. In the practice of naturopathic medicine and other alternative and complementary practices, it often seems that we have drawn an invisible line between ‘acceptable’ natural therapies and ‘unacceptable’ drug therapies. Aspirin is often viewed as on the wrong side of this line, something that we, and our patients, do not want to use. It is not natural enough. As risk of injury from using low dose aspirin has been reported to be minimal, it does not seem to be about danger either.
Given the apparent magnitude of the benefits demonstrated in this study, it may be time to consider suggesting regular aspirin to a wider population of patients, in this instance, men who have been treated for prostate cancer.
A similar study appeared last year that suggests that regular aspirin use reduces risk of breast cancer recurrence to a similar degree as reported in this study for prostate cancer. That study is reviewed in detail in an earlier newsletter:
Another article of interest is a commentary in the Natural Medicine Journal written by our dear friend Tina Kaczor ND, FABNO:
Daily Aspirin may reduce risk of cancer death January 2011 http://naturalmedicinejournal.com/article_content.asp?article=26
Reference: Choe KS, Cowan JE, Chan JM, Carroll PR, D'Amico AV, Liauw SL. Aspirin use and the risk of prostate cancer mortality in men treated with prostatectomy or radiotherapy. J Clin Oncol. 2012 Oct 1;30(28):3540-4.