- A new study suggests that low-dose aspirin therapy does not reduce overall cancer risk in older adults.
- The findings also indicate that those assigned to aspirin had a higher risk of cancer-related mortality during the trial.
- However, the results suggest that participants did not have any long-term lasting effects of cancer risk after stopping aspirin.
- Overall, the study suggests that aspirin therapy should not be used as a strategy to prevent cancer in older adults.
Aspirin is a common drug that can help relieve pain and fever. In addition, it may also have many other potential uses.
As the global population ages, there is an increase in the prevalence of age-related conditions, such as cancer. For example, more than two-thirds of all new cancers are diagnosed in those aged 60 or older. This reinforces the need to identify preventive strategies.
Previous research has suggested that aspirin may play a potential role in reducing cancer incidence and mortality, particularly for colorectal and liver cancers. However, conflicting evidence suggests aspirin may have adverse effects on older adults with cancer
A new long-term follow-up study, published in JAMA Oncology, adds to this, suggesting that aspirin therapy for cancer prevention is not recommended in older adults. The findings indicate that aspirin does not lower cancer risk, and may even increase cancer-related mortality during treatment.
The researchers followed more than 19,000 community-dwelling older adults, over a median follow-up of 8.6 years, to examine whether daily low dose aspirin affected cancer incidence or cancer-related death. They recorded 3,448 new cancer diagnoses and 1,173 cancer-related deaths.
The study found that taking 100 milligrams (mg) of aspirin daily was not associated with a reduction in overall cancer incidence compared with placebo.
Suzanne Orchard, PhD, Director of the ASPREE Extension (ASPREE-XT) study and lead author of this study spoke to Medical News Today about its findings.
“Prior studies have shown a decreased risk for some cancers with aspirin, especially for [colorectal cancer], but these studies have been conducted in middle-aged people, or in those at very high risk of [colorectal cancer] such as those with Lynch syndrome, a hereditary bowel cancer,” Orchard told us.
“Our study shows that in older people, aspirin does not provide any overall cancer prevention benefit and thus highlights that disease processes and responses to medications can differ in individuals, depending on their age,” she noted.
While taking low dose aspirin did not increase the chance of getting cancer it older adults, it was linked to a higher risk of dying from cancer. However, this higher risk was only seen while participants were actively taking aspirin during the trial.
The study found that cancer-related mortality was 15% higher among participants who had been assigned to aspirin during the randomized trial period.
This is likely due to the higher rates of late-stage cancer and cancer-related deaths among aspirin users at the end of the original ASPREE trial phase.
When researchers looked at the results over a longer time, including both the trial and the period after it ended, the higher risk of cancer-related death was still seen overall.
To determine whether aspirin had any delayed or lasting impact on cancer risk, the investigators examined outcomes after the randomized trial ended.
This analysis included nearly 15,000 participants who were cancer-free at the end of the trial and continued to be followed in an observational extension study called ASPREE-XT.
During this post-trial period, the risk did not appear to continue. This suggests that aspirin did not have long-term, or legacy effects, on cancer risk once treatment stopped.
There was some evidence of a lower risk of metastatic cancer after the trial among those originally assigned to aspirin, but this did not translate into a reduction in cancer deaths. As such, these results suggest more follow-up over a longer period is still necessary.
The findings add to growing evidence that age at aspirin initiation may be critical in determining its effects on cancer.
Studies showing cancer-preventive benefits of aspirin have largely involved younger or middle-aged adults and often required more than 10 years of follow-up to observe an effect.
In contrast, ASPREE participants began aspirin at a median age of 74. The researchers note that age-related changes, such as declining immune function, chronic low-grade inflammation, and differences in tumor biology, could reduce aspirin’s potential anti-cancer effects or even contribute to harm in older adults.
“The exact mechanism of action of aspirin in cancer is not fully understood, and hence it is hard to pinpoint why aspirin effects differ as we age,” Orchard told MNT. “However, we know the body’s immune system plays a role in its response to cancer.”
“Changes in the body as we age, such as age-related declines in immune function (called ‘immunosenescence’) and age-related low-grade chronic inflammation (called ‘inflammaging’) leading to immune system exhaustion, may attenuate aspirin’s anti-cancer effects in older people.”
– Suzanne Orchard, PhD
Although the study found that aspirin does not reduce overall cancer risk in older adults, it did identify a lower incidence of melanoma among aspirin users, both during long-term follow-up and after the trial ended.
While intriguing, particularly in Australia, where melanoma rates are high, the authors caution that this finding could be due to chance and requires further study.
“This result should be viewed with some caution, as the event numbers were low which increases the risk that this finding may be due to chance,” Orchard explained.
“Nonetheless, this is an area we will explore further, as other studies have also reported a protective effect, however, others have shown no significant reduction in melanoma risk, or in some cases, varied results between men and women,” she added.
Conversely, the study also observed higher rates of brain cancer and deaths from rare cancers among aspirin users, but these findings were based on small numbers and should be interpreted cautiously.
Overall, the results suggest that starting low-dose aspirin in older age should not be recommended for primary prevention of cancer.
While aspirin remains an important medication for certain cardiovascular conditions, its routine use for preventing cancer in otherwise healthy older adults is not supported by the evidence from this study.
Orchard notes that patients and clinicians should have considered discussions before making any decision about starting low-dose aspirin in older age.
“[A]dults ages 60 to 69 years should decide with their primary care clinician if aspirin use for primary prevention is right for them […] Similarly, the Cancer Council in Australia does not recommend taking low-dose aspirin to reduce the risk of colorectal cancer for those over 70,” Orchard added.
The researchers emphasize that longer follow-up may still be necessary to fully understand aspirin’s long-term effects. However, current evidence does not favor aspirin as a cancer-preventive strategy when initiated later in life.
“Long-term follow-up of ASPREE participants will continue to further assess the association of aspirin with cancer over a 15 year horizon, since some studies have only noted associations after 10+ years of follow-up,” Orchard told MNT.
“It should also be highlighted that individuals taking aspirin for cardiovascular disease prevention on the advice of their healthcare provider, should continue to do so,” she concluded.
