Low-Dose Aspirin Linked to Reduced Breast Cancer Recurrence, But Not Lower Mortality: Study Finds
Denmark: A large-scale Danish study suggests that long-term use of low-dose aspirin may help reduce the risk of breast cancer recurrence, although it does not appear to improve overall survival outcomes.
The study, conducted by Elisabeth Solmunde and colleagues from the Department of Clinical Epidemiology at Aarhus University and Aarhus University Hospital, examined the long-term effects of low-dose aspirin on breast cancer recurrence and mortality. The findings were published in Scientific Reports following an extensive follow-up period of up to 23 years.
Researchers analyzed data from more than 20,500 women aged 40 years and older who were diagnosed with stage I to III breast cancer between 1996 and 2004. Information regarding low-dose aspirin use was obtained through the Danish Prescription Registry, while data on cancer recurrence came from the Danish Breast Cancer Group database and a validated algorithm.
The study revealed the following findings:
- Throughout 232,000 person-years of follow-up, 4,527 women experienced a recurrence of breast cancer.
- The 20-year cumulative recurrence rate was lower among low-dose aspirin users (17.8%) compared to non-users (22.4%).
- Among women who remained disease-free for at least 10 years, aspirin users had a recurrence rate of 9.9%, compared to 12.7% in non-users.
- Aspirin use was associated with a modest reduction in recurrence risk, with a 20% lower hazard at five years post-diagnosis (adjusted HR 0.80).
- There were similar trends of reduced recurrence at 10 and 15 years; however, these were not statistically significant.
- Aspirin users had slightly higher all-cause mortality compared to non-users, with a five-year hazard ratio of 1.08.
- Comparable mortality trends were observed at the 10- and 15-year follow-ups.
"These findings suggest that while aspirin may have a protective effect against cancer recurrence, its impact on overall survival remains unclear," the researchers wrote.
Researchers noted that the increased mortality among aspirin users could be due to “confounding by indication”—meaning that individuals taking aspirin may have underlying health conditions such as cardiovascular disease, which could increase their risk of death from other causes before cancer recurrence occurs.
Given aspirin’s widespread availability, low cost, and favorable safety profile, these findings carry potential public health significance. The authors emphasized that while the results point toward a possible anti-cancer benefit of aspirin, caution is warranted in interpretation due to the influence of competing risks.
"Further insights are anticipated from upcoming pooled data from the ongoing ABC and Add-Aspirin trials, which may provide more definitive evidence regarding aspirin's role in breast cancer recurrence and survival," the authors concluded.
Reference:
Solmunde, E., Pedersen, R. N., Nørgaard, M., Mellemkjær, L., Friis, S., Ejlertsen, B., Ahern, T. P., & P., D. (2025). Association between low-dose aspirin use and breast cancer recurrence: A Danish nationwide cohort study with up to 23 years of follow-up. British Journal of Cancer, 1-9. https://doi.org/10.1038/s41416-025-03112-3
