New research by Monash University has found that taking daily low-dose aspirin will not reduce long-term cancer risk in older adults and may be associated with a higher risk of cancer-related death.

The findings, published in the JAMA Oncology journal, challenges findings from an ongoing ‘Aspree’ (ASPirin in Reducing Events in the Elderly) study that suggested aspirin reduced cancer risk after about a decade of use, particularly for colorectal cancer.

The earlier study began in 2010 and involved more than 19,000 Australian and American adults aged 70 and over who were again assessed. Participants in both studies had no prior history of cardiovascular disease events, dementia, or physical disability limiting their independence at enrolment.

During the original Aspree trial, participants were randomly assigned to receive either 100 mg of aspirin daily or a matched placebo. In the subsequent observational phase, participants stopped taking the study medication. Researchers then assessed the association between aspirin use and cancer outcomes across both phases.

First author Suzanne Orchard, an associate professor from Monash University’s School of Public Health and Preventive Medicine, said the combined median follow-up period of 8.6 years showed no difference in overall cancer incidence between those originally assigned to aspirin and those assigned to placebo.

“Whilst we found overall no change in cancer incidence risk with aspirin when initiated in older age, we found cancer mortality remained significantly elevated by 15%,” Professor Orchard said.

“However, the elevated cancer mortality risk seen with aspirin for participants in the original Aspree trial period did not persist into the post-trial Aspree Extension study, suggesting no lasting aspirin effect, although longer follow up of the cohort is warranted.”

The study also found no difference in cancer incidence when analysed by cancer stage – from stages 1 to 4 – or by extent of disease, including non-metastatic and metastatic cancers.

Based on the findings, researchers do not recommend starting low-dose aspirin later in life for cancer prevention.

“From these findings, commencing a program of low-dose aspirin for a number of years for the prevention of cancer is not recommended in older adults,” Associate Professor Orchard said.

“Individuals who are concerned about their cancer risk should speak to their doctors about the right strategy for their individual health care.”