Where does that leave aspirin for cancer prevention?
“Although these results suggest that we should be cautious about starting aspirin therapy in otherwise healthy older adults, this does not mean that individuals who are already taking aspirin – particularly if they began taking it at a younger age – should stop their aspirin regimen,” Dr. Chan said.
There are decades of data supporting the use of daily aspirin to prevent multiple cancer types, particularly colorectal cancer, in individuals under the age of 70 years. In a recent meta-analysis, for example, regular aspirin use was linked to a 27% reduced risk for colorectal cancer, a 33% reduced risk for squamous cell esophageal cancer, a 39% decreased risk for adenocarcinoma of the esophagus and gastric cardia, a 36% decreased risk for stomach cancer, a 38% decreased risk for hepatobiliary tract cancer, and a 22% decreased risk for pancreatic cancer.
While these figures are mostly based on observational and case-control studies, it “reaffirms the fact that, overall, when you look at all of the ages, that there is still a benefit of aspirin for cancer,” John Cuzick, PhD, of Queen Mary University of London (England), said in an interview.
In fact, the meta-analysis goes as far as suggesting that perhaps the dose of aspirin being used is too low, with the authors noting that there was a 35% risk reduction in colorectal cancer with a dose of 325 mg daily. That’s a new finding, Dr. Cuzick said.
He noted that the ASPREE study largely consists of patients 70 years of age or older, and the authors “draw some conclusions which we can’t ignore about potential safety.”
One of the safety concerns is the increased risk for gastrointestinal bleeding, which is why Dr. Cuzick and colleagues previously recommended caution in the use of aspirin to prevent cancer in elderly patients. The group published a study in 2015 that suggested a benefit of taking aspirin daily for 5-10 years in patients aged 50-65 years, but the risk/benefit ratio was unclear for patients 70 years and older.
The ASPREE data now add to those uncertainties and suggest “there may be some side effects that we do not understand,” Dr. Cuzick said.
“I’m still optimistic that aspirin is going to be important for cancer prevention, but probably focusing on ages 50-70,” he added. “[The ASPREE data] reinforce the caution that we have to take in terms of trying to understand what the side effects are and what’s going on at these older ages.”
Dr. Cuzick is currently leading the AsCaP Project, an international effort to better understand why aspirin might work in preventing some cancer types but not others. AsCaP is supported by Cancer Research UK and also includes Dr. Chan among the researchers attempting to find out which patients may benefit the most from aspirin and which may be at greater risk of adverse effects.
The ASPREE trial was funded by grants from the National Institute on Aging, the National Cancer Institute, the National Health and Medical Research Council of Australia, Monash University, and the Victorian Cancer Agency. Several ASPREE investigators disclosed financial relationships with Bayer Pharma. The editorialists had no conflicts of interest. Dr. Cuzick has been an advisory board member for Bayer in the past.
SOURCE: McNeil J et al. J Natl Cancer Inst. 2020 Aug 11. doi: 10.1093/jnci/djaa114.