Drug thought to curb spread of disease through the body

Aspirin may halve the risk of death from breast cancer in women who have had early treatment for the disease, researchers have found.

The effect was revealed in an analysis of data from the US Nurses' Health Study, which followed 238,000 nurses in the US for more than 30 years. It is the first time aspirin has been shown to significantly reduce the risk of death from breast cancer in women who have already been treated for the disease.

Michelle Holmes, associate professor of medicine and epidemiology at Harvard Medical School, who led the study published in the Journal of Clinical Oncology, said: "If these findings are confirmed in other clinical trials, taking aspirin may become another simple, low-cost and relatively safe tool to help women with breast cancer live longer, healthier lives."

Previous studies have suggested aspirin has a protective effect against breast cancer, as well as at least two other types of cancer: prostate and colon. Researchers on the latest study say it is not clear how it affects cancer cells but it may curb the spread of the disease by reducing inflammation, which is a key factor in cancer development.

The results showed that in addition to halving the risk of death, it also reduces metastases – spread of the cancer to other areas of the body – by a similar margin. Laboratory studies indicate that aspirin reduces the growth and invasiveness of breast cancer cells.

Of the 4,164 women in the study who had been treated for breast cancer between 1976 and 2002, 400 had developed metastases and 341 had died. Women who took aspirin two to five days a week had a 71 per cent lower risk of dying from breast cancer and a 60 per cent reduced chance of the cancer spreading.

Women who took an aspirin daily had similar but slightly lower reductions in their risk. No details of dose were collected but the researchers say most of those who took a regular aspirin did so to prevent heart disease and were using a low dose of 81mg a day.

The study's authors warn women not to take aspirin during treatment for breast cancer, because of the risk of potential interactions that can increase side-effects. Aspirin can also cause stomach irritation and bleeding, which can be serious and lead to long-term problems such as ulcers.

Lori Pierce, of the American Society of Clinical Oncology's cancer communications committee, said: "Several studies have suggested that aspirin may have beneficial effects against cancer because of its anti-inflammatory effects. But aspirin can cause stomach bleeding and is not for everyone.

"These are promising findings, and if they are confirmed in additional clinical trials, physicians may be able to regularly recommend aspirin to their breast cancer patients to reduce risk of cancer spread and mortality."

Ed Yong, head of health information at Cancer Research UK, said: "Several studies have found that taking aspirin and other related drugs is associated with a lower risk of breast cancer, and this new study suggests that they might also help to stop cancer from spreading and improve a woman's chances of survival.

"But aspirin has risks as well as benefits... So we need large clinical trials to see if it can really save lives from breast cancer, and, if so, to work out what doses to use and how long to use the drugs for."