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Long-Term ASPREE Study Finds No Benefit of Low-Dose Aspirin for Cancer Prevention in Older Adults

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Daily Aspirin: No Long-Term Cancer Prevention Benefit for Older Adults, ASPREE-XT Study Finds

New findings from the extended Aspirin in Reducing Events in the Elderly (ASPREE) study, known as ASPREE-XT, indicate that daily low-dose aspirin may not provide long-term cancer prevention benefits for older adults. This research extends previous observations from the initial ASPREE trial.

Key Findings from ASPREE-XT

The initial ASPREE trial, with a median follow-up of 4.7 years, reported no difference in cancer incidence between aspirin and placebo groups. The ASPREE-XT observational extension now provides a longer-term perspective.

With a median follow-up of 8.6 years, the ASPREE-XT study similarly found no association between aspirin use and overall cancer incidence in older adults.

  • After 8.6 years, no association was observed between low-dose aspirin and overall cancer incidence (hazard ratio 0.98, 95% confidence interval 0.92-1.05).
  • No association was found with all solid tumors (HR 0.99, 95% CI 0.92-1.06) or stage-specific levels. This includes specific findings for prostate, colorectal, breast, lung, and bladder cancer incidence.
  • A potential protective association was noted between aspirin and melanoma incidence (HR 0.77, 95% CI 0.62-0.94).

Mortality and Previous Research Outcomes

Individuals in the aspirin group were 15% more likely to die following an incident cancer event compared to the placebo group. This elevated risk was lower than observed at the end of the clinical trial phase and dissipated when participants were no longer taking study medication, suggesting it was a residual effect from the trial phase.

Over the past decade, research from ASPREE and ASPREE-XT has indicated no association between daily low-dose aspirin and various other outcomes in older adults, including:

  • Promoting a healthy lifespan.
  • Reducing all-cause mortality (it increased by 14%).
  • Reducing stroke risk (increased intracranial bleeding risk).
  • Reducing fracture risk (increased serious falls risk).
  • Reducing major gastrointestinal bleeds (increased risk).
  • Reducing major adverse cardiovascular events (increased risk of major hemorrhage).
  • Slowing the decline in global cognition, kidney function, or hearing loss.
  • Reversing frailty.

However, daily low-dose aspirin was found to reduce the incidence of type 2 diabetes.

Medical Recommendations and Biological Factors

Associate Professor Suzanne Orchard, lead author of the new research and director of the ASPREE-XT study, stated: "Older adults should avoid initiating daily aspirin for primary prevention." She further noted that evidence supporting aspirin's benefits largely comes from middle-aged cohorts, with recent trials on older populations (ASPREE, ARRIVE, ASPIRE) showing different outcomes.

The researchers suggest that age-related biological changes may attenuate aspirin's anti-tumoral effects in older adults. These changes include declines in immune function (immunosenescence) and chronic inflammation (inflammaging). Changes in cancer biology pathways with age might also influence aspirin's response.

Changing Guidelines for Aspirin Use

Medical organizations are revising their guidelines regarding aspirin use for primary prevention in light of evolving research:

  • Australian Cancer Council: Previously recommended low-dose aspirin for older adults. It now restricts this recommendation to ages 60-69, advising discussion with a clinician for those over 70.
  • US Preventive Services Task Force (USPSTF): In 2016, the USPSTF recommended low-dose aspirin for colorectal cancer prevention. In 2022, this recommendation was withdrawn for individuals over 70, citing a lack of benefit and potential risk in this demographic. The USPSTF has requested more research on low-dose aspirin and colorectal cancer in people over 70, with follow-up periods exceeding 10 years.

Future Research: ASPREE-LT

Plans are underway for ASPREE-LT (long-term), a third phase of the study, funded by the National Cancer Institute in the US. This extension will follow participants for another five years, aiming for more than 15 years of total follow-up to provide further evidence on long-term effects.

Important Caveat

The study's results are specific to older individuals initiating aspirin for primary cancer prevention. Individuals prescribed aspirin by a healthcare provider for secondary cardiovascular disease prevention should not discontinue treatment without consulting their doctor.