STUDY:

JOURNAL: Journal of the American Medical Association

AUTHORS: Christine Velicer

ABSTRACT: Women who use antibiotics to treat infections may be increasing their risk of breast cancer, a US study has suggested.

COMMENTARY: Researchers found that women who used the drugs for up to 500 days were about 1.5 times as likely to develop cancer. Among higher users, the risk of death from the disease was nearly 3.5 times as great.

The association between disease and death was even stronger among those who used antibiotics for longer, although the authors of a report in the Journal of the American Medical Association stressed that more research was needed to establish whether the apparent association was causal or if other factors needed to be considered.

These included the possibility that immune systems were already undermined by conditions for which antibiotics were being taken or that inflammation of tissues linked to some conditions made them more suitable breeding grounds for tumours.

Scientists are already concerned about the excessive use of antibiotics to treat infections, blaming it for growing bacterial resistance to drugs.

The study, led by Christine Velicer of Washington University, Seattle, compared medical data for 2,266 women who had breast cancer with 7,953 women who did not.

In the report on their work, the researchers said: "While the implications for clinical practice will not be clear until additional studies are conducted, the results of this study support the continued need for prudent long-term use of antibiotics."