No overall association seen between postdiagnosis low-dose aspirin, prostate cancer mortality
Data were collected from a nationwide Danish registry on tumor characteristics, drug use, primary prostate cancer therapy, comorbid conditions, and socioeconomic variables for men with incident prostate adenocarcinoma between 2000 and 2011.
Low-dose aspirin after prostate cancer diagnosis does not appear to have an overall effect on mortality, but slight reductions in mortality with aspirin use were seen after five years, according to a new study.
Researchers in Denmark performed a nationwide cohort study to examine whether postdiagnosis use of low-dose aspirin was associated with death from prostate cancer. Data were collected from a nationwide registry on tumor characteristics, drug use, primary prostate cancer therapy, comorbid conditions, and socioeconomic variables for men with incident prostate adenocarcinoma between 2000 and 2011. Researchers defined postdiagnosis use of low-dose aspirin as two or more prescriptions for 75 to 150 mg filled within a year after prostate cancer diagnosis. (Although aspirin is available over the counter in Denmark, most low doses are dispensed by prescription, they noted.)
Follow-up began one year after diagnosis and ended at death, emigration from Denmark, or Dec. 31, 2015. The study's primary outcomes were prostate cancer-specific mortality and mortality from other causes. Aspirin exposure periods of five and 7.5 years were examined in secondary analyses. Results were published March 5 by Annals of Internal Medicine.
Overall, 29,136 patients were included in the study, with a median age of 70 years at prostate cancer diagnosis. During a median follow-up of 4.9 years through 2015, 7,633 patients died of prostate cancer and 5,575 died of other causes. Use of low-dose aspirin after prostate cancer diagnosis was associated with adjusted hazard ratios of 0.95 (95% CI, 0.89 to 1.01) for prostate cancer-specific mortality and 1.12 (95% CI, 1.05 to 1.20) for death from other causes. Hazard ratios for prostate cancer mortality did not appear to vary substantially by clinical stage or primary therapy. However, a reduction in death from prostate cancer was associated with aspirin use in men with low Gleason scores (hazard ratio, 0.82; 95% CI, 0.70 to 0.97). In secondary analyses, a slight reduction was seen in prostate cancer mortality with use of low-dose aspirin at five years (hazard ratio, 0.91; 95% CI, 0.83 to 1.01) and 7.5 years (hazard ratio, 0.84; 95% CI, 0.72 to 0.97) after diagnosis.
The researchers noted that no data were available on over-the-counter aspirin use, that data on some prognostic factors were incomplete, and that some causes of death may have been misclassified, among other limitations. They concluded that their study did not support an overall effect of low-dose aspirin use after prostate cancer diagnosis on death from prostate cancer but that an inverse association might be present five years after cancer diagnosis and in men with low Gleason scores.
The authors of an accompanying editorial said that the study supports the idea that aspirin use doesn't appear to reduce overall risk for death from prostate cancer at the population level but raises the possibility that tumor grade misclassification may differ between patients who take aspirin and those who do not. “To determine definitively whether long-term aspirin use improves prostate cancer outcomes, future research should evaluate aspirin exposures longer than those studied to date and investigate the effects of aspirin exposure on disease classification,” the editorialists wrote.