Men who have used aspirin regularly face a lower risk of lethal prostate cancer than men who haven’t, according to findings from the Physicians’ Health Study (PHS).
“There seems to be a stronger association between regular aspirin use and reduced risk of lethal prostate cancer at later points of tumor progression, evidenced by results from our analyses stratified on PSA era and stage at diagnosis,” said Dr. Mary K. Downer from Harvard T. H. Chan School of Public Health in Boston.
“If this association is indeed causal - which we do not yet know - this could have important implications for managing later stage disease,” she told Reuters Health by email. “It would imply that aspirin may prevent tumor metastasis to other organs rather than tumor initiation, which is arguably more clinically important.”
Previous studies have yielded conflicting results on the association between regular aspirin use and overall and advanced prostate cancers. There is little information on the relationship between aspirin use and lethal prostate cancer.
Dr. Downer’s team used data from more than 22,000 participants in the PHS to investigate the possible association between regular aspirin use (more than three days/week for at least one year) and lethal prostate cancer.
Compared with never use, past regular aspirin use was associated with a 46% lower risk of lethal prostate cancer and current use was associated with a 32% lower risk of lethal prostate cancer, the researchers report in European Urology, online February 8.
Men who currently used aspirin after diagnosis of nonmetastatic disease had 32% lower risk of lethality and 28% lower overall mortality, compared with never users, whereas past postdiagnostic use was associated with nonsignificantly higher risks of lethality and overall mortality.
Associations between aspirin and reduced lethality and between current postdiagnostic aspirin and improved survival did not hold for cases diagnosed in the PSA era.
“Evidence on associations between aspirin and the actual initiation of prostate cancer tumors is mixed, and our results suggest that regular aspirin and total prostate cancer incidence are not associated,” Dr. Downer said. “Furthermore, prostate cancer incidence as an outcome is of questionable clinical significance. Autopsy studies show that many men die with prostate cancer without ever knowing that they had it.”
“The more important question is whether aspirin prevents prostate cancer progression to harmful (metastatic or fatal) disease,” she said. “While our results suggest that it may, they should not influence treatment plans for prostate cancer patients just yet. For now, our results should be used to guide future research in this area.”
“We are conducting a similar analysis in an independent population (Health Professionals Follow-Up Study),” Dr. Downer said. “If our findings are validated here, this will also strengthen the evidence. A randomized trial of aspirin among prostate cancer patients would be strong evidence for (or against) aspirin's potential benefits, and our results suggest that a trial may be warranted.”
She added, “It is worth noting that the U.S. Preventive Services Task Force recommends aspirin use in men and women ages 55-79 due to its potential protective effects against myocardial infarction; several other studies suggest that aspirin may reduce risk of other cancers.”