medwireNews: A Danish study has found no protective effect of low-dose aspirin taken after diagnosis on prostate cancer-specific mortality (PCSM), while South Korean research has identified a link between long-term use of the nonsteroidal anti-inflammatory drug and a reduced risk for incident lung cancer.
Commenting on the findings, Janusz Jankowski (University Hospitals of Morecambe Bay NHS Trust, UK) told medwireNews that where the use of aspirin in the setting of cancer is concerned the “Goldilocks effect prevails.”
Too much or too little, in terms of dose or duration, can result in a risk–benefit ratio that is not optimal, he said, noting that “the risks are present for gastrointestinal bleeding especially if no acid suppressing drug is used.”
Jankowski continued: “In addition using aspirin in the wrong setting or people means the effect doesn't register either.”
The first study was based on Danish registry data and included 29,136 men who had been diagnosed with prostate adenocarcinoma between 2000 and 2011. Nearly a quarter (24.6%) had filled at least two prescriptions for low-dose (75–150 mg) aspirin in the year after diagnosis and were considered postdiagnosis users.
As reported in the Annals of Internal Medicine, 7633 deaths were attributable to prostate cancer during a median follow-up of 4.9 years, where follow-up started from 1 year postdiagnosis.
After adjusting for a raft of confounders – including demographic variables, Gleason score, primary prostate cancer therapy, concomitant medications, and comorbidities – there was no significant association between low-dose aspirin use and PCSM (hazard ratio [HR]=0.95).
However, in subgroup analyses, postdiagnosis use of aspirin was associated with a significantly reduced risk for PCSM in patients with a Gleason score no higher than 6 (HR=0.82), while the risk was increased for those who received brachytherapy as primary therapy (HR=1.81).
And a secondary analysis suggested that survival was improved for aspirin users with longer exposure times of 5.0 and 7.5 years, with an HR for PCSM of 0.91 and 0.84, respectively, relative to nonusers.
These findings suggest that “a potential effect of low-dose aspirin use on prostate cancer mortality requires several years to appear,” say Charlotte Skriver (Danish Cancer Society, Copenhagen) and co-authors.
For the second study, Eun Mi Chun (Ewha Womans University, Seoul) drew on the Korean National Health Information Database to identify 12,969,400 individuals aged 40–84 years who did not have a diagnosis of lung cancer in 2006–2010 and who had not received a longer than 6-month prescription of standard-dose (≥325 mg) aspirin between 2002–2010.
Over 63,787,432.9 person–years of follow-up, 0.5% of participants developed incident lung cancer, which equated to an incidence rate of 98.8 per 100,000 person–years.
Use of low-dose aspirin – defined as a prescription for a 100 mg or lower dose for at least 104 days per year – for 5 years or more was associated with a significantly reduced risk for lung cancer after accounting for factors such as age, sex, smoking, alcohol consumption, BMI, and family history of cancer.
Specifically, the adjusted HRs for lung cancer risk were 0.96, 0.94, and 0.89 for 5–6, 7–8, and 9 years of aspirin use, respectively, versus no use.
Of note, the results were similar across the subgroups, except in people aged less than 65 years and those with diabetes, among whom there appeared to be no significant decrease in lung cancer risk with longer use of aspirin.
The researchers therefore summarize in JAMA Network Open that “the use of low-dose aspirin for more than 5 years was associated with a modest risk reduction of incident lung cancer.”
But in light of the limitations of the study – including the retrospective, nonrandomized design – they stress that “further prospective studies are needed to establish whether a causal association exists between aspirin use and risk of lung cancer.”
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