Researchers in Manchester are leading the first clinical trial to test whether aspirin can help treat an aggressive form of breast cancer.
The cheap and widely-available drug is being trialled as part of a potential new treatment.
Researchers hope aspirin could work well when combined with immunotherapy for patients with triple negative breast cancer.
The trial, funded by the Breast Cancer Now Catalyst Programme, which aims to speed up progress in research through innovation and collaboration, is the first clinical study to test if aspirin can make tumours more sensitive to immunotherapy in patients.
The research, led by Dr Anne Armstrong from the Christie NHS Foundation Trust in Manchester, will trial the drug avelumab both with and without aspirin before patients receive surgery and chemotherapy treatment.
Breast Cancer Now said successful results could lead to further clinical trials of aspirin and avelumab for incurable secondary triple negative breast cancer, which happens when cancer cells that started in the breast spread to other parts of the body.
There are around 8,000 women diagnosed with triple negative breast cancer in the UK each year, the charity said.
It is a less common but often more aggressive type of breast cancer that disproportionately affects younger women and black women, the organisation added.
Announcing the trial today Dr Armstrong, a consultant medical oncologist and honorary senior lecturer at the Christie NHS Foundation Trust, said: "Our earlier research has suggested that aspirin can make certain types of immunotherapy more effective by preventing the cancer from making substances that weaken the immune response.
"Anti-inflammatory drugs like aspirin could hold the key to increasing the effectiveness of immunotherapy when used at the same time.
"Trialling the use of a drug like aspirin is exciting because it is so widely available and inexpensive to produce.
"We hope our trial will show that, when combined with immunotherapy, aspirin can enhance its effects and may ultimately provide a safe new way to treat breast cancer.
Dr Simon Vincent, director of research, support and influencing at Breast Cancer Now, added: "The 8,000 women diagnosed with triple negative breast cancer in the UK each year face the frightening reality of limited treatment options.
"We urgently need to address this.
"Research has already suggested aspirin could improve outcomes for many cancer patients and we hope that Dr Armstrong's trial will show the same to be true for patients with triple negative breast cancer, so that we can prevent more lives being lost to this devastating disease."
Breast Cancer Now said pharmaceutical giant Pfizer has provided the charity with funding through an independent medical research grant and given its researchers access to several Pfizer medicines.
The Christie is the largest single site cancer centre in Europe.
