BACKGROUND: ASPirin in Reducing Events in the Elderly, a randomized, double-blind, placebo-controlled trial of daily low-dose aspirin (100 mg) in older adults, showed an increase in all-cause mortality, primarily due to cancer. In contrast, prior randomized controlled trials, mainly involving younger individuals, demonstrated a delayed cancer benefit with aspirin. We now report a detailed analysis of cancer incidence and mortality.
METHODS: 19 114 Australian and US community-dwelling participants aged 70 years and older (US minorities 65 years and older) without cardiovascular disease, dementia, or physical disability were randomly assigned and followed for a median of 4.7 years. Fatal and nonfatal cancer events, a prespecified secondary endpoint, were adjudicated based on clinical records.
RESULTS: 981 cancer events occurred in the aspirin and 952 in the placebo groups. There was no statistically significant difference between groups for all incident cancers (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 0.95 to 1.14), hematological cancer (HR = 0.98, 95% CI = 0.73 to 1.30), or all solid cancers (HR = 1.05, 95% CI = 0.95 to 1.15), including by specific tumor type. However, aspirin was associated with an increased risk of incident cancer that had metastasized (HR = 1.19, 95% CI = 1.00 to 1.43) or was stage 4 at diagnosis (HR = 1.22, 95% CI = 1.02 to 1.45), and with higher risk of death for cancers that presented at stages 3 (HR = 2.11, 95% CI = 1.03 to 4.33) or 4 (HR = 1.31, 95% CI = 1.04 to 1.64).
CONCLUSIONS: In older adults, aspirin treatment had an adverse effect on later stages of cancer evolution. These findings suggest that in older persons, aspirin may accelerate the progression of cancer and, thus, suggest caution with its use in this age group.
Follow-up was short but the benefits appear to outweigh the risk.
In this RCT, 10000 patients who were mostly > 70 years-old received low-dose aspirin and 10000 received placebo. Aspirin was associated with a higher risk for solid organ metastatic cancer, but the increased risk was small.
As an Internist, I think this study is very relevant as so many patients take aspirin on their own or given by their physicians. This throws light on the fact that medications should be used with caution unless there is a very strong indication backed up by robust data.
Definitely an evolving area of research.
Since this is based on a large RCT, the results are more likely to be valid than are the results from observational studies.
Unexpected results of the ASPREE RCT contradicted previous RCTs and meta-analysis on the effect of low-dose aspirin and shows it has a higher overall mortality attributable to death from cancer. This detailed analysis of the ASPREE data confirms that, in healthy elderly patients over 70 years of age, low-dose aspirin increases the incidence of solid cancers and mortality from both localized and advanced cancers.
This is important in getting true consent for treatment. Low-dose aspirin was viewed as either of no benefit or only good. Its use is ubiquitous and needs to be reassessed in light of these data. This clearly undermines previously held beliefs.