Aspirin may accelerate the progression of advanced cancers and lead to an earlier death as a result, new data from the ASPREE study suggest.
The results showed that patients 65 years and older who started taking daily low-dose aspirin had a 19% higher chance of being diagnosed with metastatic cancer, a 22% higher chance of being diagnosed with a stage 4 tumor, and a 31% increased risk of death from stage 4 cancer, when compared with patients who took a placebo.
John J. McNeil, MBBS, PhD, of Monash University in Melbourne, Australia, and colleagues detailed these findings in the Journal of the National Cancer Institute.
“If confirmed, the clinical implications of these findings could be important for the use of aspirin in an older population,” the authors wrote.
When results of the ASPREE study were first reported in 2018, they “raised important concerns,” Ernest Hawk, MD, and Karen Colbert Maresso wrote in an editorial related to the current publication.
“Unlike ARRIVE, ASCEND, and nearly all prior primary prevention CVD [cardiovascular disease] trials of aspirin, ASPREE surprisingly demonstrated increased all-cause mortality in the aspirin group, which appeared to be driven largely by an increase in cancer-related deaths,” wrote the editorialists, who are both from the University of Texas MD Anderson Cancer Center in Houston.
Even though the ASPREE investigators have now taken a deeper dive into their data, the findings “neither explain nor alleviate the concerns raised by the initial ASPREE report,” the editorialists noted.
ASPREE design and results
ASPREE is a multicenter, double-blind trial of 19,114 older adults living in Australia (n = 16,703) or the United States (n = 2,411). Most patients were 70 years or older at baseline. However, the U.S. group also included patients 65 years and older who were racial/ethnic minorities (n = 564).
Patients were randomized to receive 100 mg of enteric-coated aspirin daily (n = 9,525) or matching placebo (n = 9,589) from March 2010 through December 2014.
At inclusion, all participants were free from cardiovascular disease, dementia, or physical disability. A previous history of cancer was not used to exclude participants, and 19.1% of patients had cancer at randomization. Most patients (89%) had not used aspirin regularly before entering the trial.
At a median follow-up of 4.7 years, there were 981 incident cancer events in the aspirin-treated group and 952 in the placebo-treated group, with an overall incident cancer rate of 10.1%.
Of the 1,933 patients with newly diagnosed cancer, 65.7% had a localized cancer, 18.8% had a new metastatic cancer, 5.8% had metastatic disease from an existing cancer, and 9.7% had a new hematologic or lymphatic cancer.
A quarter of cancer patients (n = 495) died as a result of their malignancy, with 52 dying from a cancer they already had at randomization.
Aspirin was not associated with the risk of first incident cancer diagnosis or incident localized cancer diagnosis. The hazard ratios were 1.04 for all incident cancers (95% confidence interval, 0.95-1.14) and 0.99 for incident localized cancers (95% CI, 0.89-1.11).
However, aspirin was associated with an increased risk of metastatic cancer and cancer presenting at stage 4. The HR for metastatic cancer was 1.19 (95% CI, 1.00-1.43), and the HR for newly diagnosed stage 4 cancer was 1.22 (95% CI, 1.02-1.45).
Furthermore, “an increased progression to death was observed amongst those randomized to aspirin, regardless of whether the initial cancer presentation had been localized or metastatic,” the investigators wrote.
The HRs for death were 1.35 for all cancers (95% CI, 1.13-1.61), 1.47 for localized cancers (95% CI, 1.07-2.02), and 1.30 for metastatic cancers (95% CI, 1.03-1.63).
“Deaths were particularly high among those on aspirin who were diagnosed with advanced solid cancers,” study author Andrew Chan, MD, of Massachusetts General Hospital in Boston, said in a press statement.
Indeed, HRs for death in patients with solid tumors presenting at stage 3 and 4 were a respective 2.11 (95% CI, 1.03-4.33) and 1.31 (95% CI, 1.04-1.64). This suggests a possible adverse effect of aspirin on the growth of cancers once they have already developed in older adults, Dr. Chan said.