Daily low-dose aspirin therapy inhibits platelet aggregation and is therefore an essential component in the treatment of cardiovascular patients. Cancer-preventative efficacy has been attested for ASA several times. Three new studies done by researchers led by Peter Rothwell of Oxford University have shown even more: a multi-year aspirin therapy not only prevents cancer and such related deaths, it also protects against the formation of metastases. The risk of frequent occurance of bleeding drops during treatment after three years (Lancet Oncology 2012).
Less bleeding, less cancer after three years
In their first study, a meta-analysis of 51 studies, the researchers, where a daily low-dose therapy was employed as a primary prevention of cardiovascular diseases, demonstrated a reduction of 15 percent in cancer deaths for women and men compared with patients not receiving aspirin. With a three-year intake, the risk of death decreases by 25 percent and at five years by as much as 37 percent. Non-cardiovascular incidence of death was also reduced. Although it’s true that the achieved reduction in cardiovascular events associated with aspirin was initially overshadowed by an increased bleeding risk, this effect nonetheless decreased with time. The outcome of three-year treatment gave an overall advantage in favour of the lowered cancer mortality.
Especially with adenocarcinoma – metastases are rare
A second study done by the scientists involving the analysis of data from five studies showed that an intake of at least 75 mg ASA per day also affects the formation of cancer metastases over the course of 6.5 years. The risk of cancer with distant metastases was reduced by 36 percent, that for the development of adenocarcinoma by 46 percent. Patients with adenocarcinoma who had not initially developed metastases benefited from aspirin and their risk of metastases decreased by 70 percent.
The third study compared the results of observational studies and randomised studies in order to track down the relationship between ASA and the occurrence of rarer cancers, which are represented in random-based studies only in small numbers. Long-term observations in this area are much more promising. It was found that daily aspirin therapy also lowers the long-term risk of rarer cancers and the formation of metastases.
ASA – medicine for your life?
Andrew Chan and Nancy Cook from Harvard Medical School in Boston, Massachusetts point out the boundaries of the study: the largest available randomised primary prevention trials, the Women’s Health Study (involving almost 40,000 participants who for ten years received ASA every other day) and the Physicians’ Health Study (with approximately 22,000 men participating and also receiving an every-second-day ASA treatment over five years) remain excluded from the analysis due to the non-daily administration mode used. These studies, however, showed no lower risk of colon cancer or other types of cancer or of cancer mortality. Limitations of the analysis also result from the number of randomised studies used in studying the frequency of occurrence of cancer. There were only six studies. In addition, studies were designed to examine cardiovascular endpoints and included no screening tests for cancer.
It seems therefore premature for the development of new guidelines, since individual advantages and disadvantages of ASA therapy must always be considered. For people with no increased cancer risk, ASA is currently no suitable prophylactic. It is also unclear which dose provides protection. Experts warn against self-medication.