International collaboration sheds light on how aspirin prevents cancer
11 Dec 2025
A new article describing how aspirin works to prevent cancer has been published today in The New England Journal of Medicine.
Aspirin is a common, low-cost medicine. Large population studies have shown that it can prevent cancers from growing or spreading, particularly those that arise from the gastrointestinal tract, such as stomach and bowel cancers. However, the way aspirin works to reduce the risk of developing cancer is not fully understood. This means that we don’t know yet who might benefit most from aspirin for cancer prevention.
The review, written by Professor Ruth Langley from University College London (UCL) and Professor Sir John Burn from the University of Newcastle, describes the work of the newly formed Suppressing Platelet Activation to Reduce Cancer (SPARC) collaboration. SPARC is an international, multi-disciplinary group led by UCL and funded by Cancer Research UK. Its focus is to understand how aspirin can be best used to prevent cancer. The group brings together experts in aspirin pharmacology, cutting edge molecular genetics and clinical researchers to focus on answering the question: “How does aspirin prevent cancer?”
Recent findings from the SPARC group have shown that aspirin can prevent cancer by suppressing the activation of platelets, which are a type of blood cell. The main function of platelets is to help blood to clot, but they also have other functions. When platelets become “activated” they change their shape and can support the growth of cancer cells in several ways. The researchers found that low-dose aspirin (75-100 mg daily) can suppress the activation of platelets and this is responsible for preventing new tumours from growing and reduces the spread of the cancer to other parts of the body (metastases). Studies in mice have found that when platelets are activated, they increase inflammation and can promote the growth of new tumours. Activated platelets also stop the immune system from removing cancer cells once they have spread beyond the original tumour.
Professor Sir John Burn said, “The recent long-term results from the CAPP-3 trial showing that low-dose aspirin, 100 mg daily, is as effective as higher doses in preventing hereditary Lynch Syndrome cancers strengthen our hypothesis that the effect of aspirin on platelets is central to understanding how aspirin prevents cancer. Patients with Lynch Syndrome should talk to their doctors about taking low-dose aspirin”.
Tracy Smith, Trustee of Lynch Syndrome UK said, “For families living with hereditary cancer risk, this research offers real hope. Understanding how aspirin works to suppress platelet activation means we are closer to knowing who can benefit most, and how to use it safely. Every step forward gives patients more confidence, more choices, and more time—and that is invaluable”.
Professor Ruth Langley said, “We are very excited about this new collaboration. As well as focussing on the mechanism of action, we are bringing together clinical trial data from across the world from patients taking aspirin after a cancer diagnosis.
Our Add-Aspirin trial is exploring whether aspirin can lower the risk of certain cancers from coming back. Preliminary results from the trial found that participants showed increased levels of platelet activation for several months after their cancer treatment. This observation motivated the formation of the SPARC collaboration. In addition, recent results from the ALASSCA trial in Sweden suggest that we can identify patients most likely to benefit from aspirin after surgery based on the genetic characteristics of their cancers. A similar analysis of Add-Aspirin participants with colorectal cancer is underway.
However, further work is still required to fully understand the relationship between platelet activation and cancer prevention. Aspirin does increase the risk of bleeding and individuals should not start taking regular aspirin without first discussing it with a healthcare professional”.
Charlotte Avery, one of the patient and public involvement partners on the project, said, “Research such as this brings reassurance that new preventive options are being explored. By exploring this link, the SPARC study could help identify a simple and widely accessible approach to cancer prevention."
First SPARC collaboration meeting held in London, April 2025. Photo credit: Paola Patrignani
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