However, the treatment – particularly with frequency of at least three times a week – is associated with reductions in mortality in bladder cancer and breast cancer, new observational research shows.
“The results presented here add to the accumulating evidence that aspirin may improve survival for some cancers,” the authors write in their cohort study that uses data from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The new research was published online Jan. 15 in JAMA Network Open.
“Although prior research has been most heavily concentrated in gastrointestinal cancers, our analysis extends the advantages associated with aspirin use to other cancers, such as bladder and breast cancers,” they explained.
In commenting on the study, John J. McNeil, MBBS, PhD, head of the department of epidemiology and preventive medicine at Monash University in Melbourne, said the findings, though intriguing, are not necessarily conclusive.
“The data was derived from a very large and well-conducted study,” Dr. McNeil, who has led other research on aspirin use and the elderly, said in an interview.
“But these conclusions were drawn from the observational component of the study and therefore potentially confounded by other characteristics that differentiate aspirin users from nonusers.”
Aspirin/cancer research in older people lacking
With well-known reports of decreased risks of heart disease, stroke, cancer – particularly gastrointestinal cancers – and all-cause mortality, as many as 25%-50% of adults in the U.S. report taking aspirin daily or every other day.
However, evidence of the benefits relating to cancer, specifically in older people, has been inconsistent, with one recent notable study, the randomized, double-blind ASPREE trial, showing no effect of aspirin on cancer incidence, but a higher mortality rate in elderly patients randomly assigned to aspirin for primary prevention.
To further investigate the effects in older patients, first author Holli A. Loomans-Kropp, PhD, and colleagues with the National Cancer Institute evaluated data on patients who were either 65 years or older at baseline or who had reached aged 65 during follow-up in the PLCO Cancer Screening Trial, which had enrollment from 1993 to 2001.
The authors identified 139,896 individuals with a mean age at baseline of 66.4 years; about half were women and 88.5% were non-Hispanic White.
Follow-up took place until the time of death, December 2014 for those who consented to follow-up, or December 2009 for those who refused consent to follow-up. The authors reported that there were 32,580 incident cancers, including 5.4% bladder, 14% breast, 1% esophageal, 1.2% gastric, 2.7% pancreatic, and 2.2% uterine cancers.
The study showed no association between aspirin use and the incidence of any of the cancer types included in the study among those over age 65.
However, further multivariate analysis of survival showed that, with follow-up adjusted to until the time of death, Dec. 31, 2015, or earlier refusal to consent, the use of aspirin at least three times per week was associated with reduced mortality in those with bladder (hazard ratio, 0.67) and breast (HR, 0.75) cancers, whereas no significant associations were observed with esophageal, gastric, pancreatic, or uterine cancer.
A similar association of any aspirin use (less than three times per week) with bladder (HR, 0.75) and breast (HR, 0.79) cancer survival was observed, the authors noted.
“These results may indicate that, for some cancer types, any aspirin use may be advantageous; however, greater benefit may be observed with increased frequency of use,” the authors wrote.