Antibiotics could increase risk of breast cancer: study

Using antibiotics could increase a patient's risk of being diagnosed with breast cancer, researchers in the US have claimed today.

The study, which is published this week in the Journal of the American Medical Association (JAMA), involved more than 10,000 women enrolled in Group Health Cooperative over an average of 17 years.

And according to a new study conducted by the Group Health Cooperative’s Center for Health Studies, the University of Washington, Fred Hutchinson Cancer Research Center, and the National Cancer Institute, the more antibiotics women took, the more likely they were to develop breast cancer.

The researchers discovered that women who took antibiotics for more than 500 days (or more than 25 individual prescriptions) during their enrollment at Group Health had twice the risk of breast cancer as those who had taken no antibiotics. Women who had between one and 25 prescriptions were about one and a half times more likely to get breast cancer than those who took no antibiotics.

However, the report's authors have said that more research is needed to confirm whether antibiotics are at increased risk of breast cancer.

Lead author Dr Christine Velicer said: "It may be that women who take a lot of antibiotics have some other processes happening in their bodies—such as a weak immune response or a hormonal imbalance—which may be an underlying cause of breast cancer."

She added: "Women who have had no antibiotic use may be a uniquely healthy group in terms of general wellbeing or lifestyle characteristics, and this possibly could account for some — but probably not all — of the increased breast cancer risk we saw among antibiotic users."

Director of the Public Health Sciences Division at Fred Hutchinson Cancer Research Center, and co-author of the study, Dr John Potter, said antibiotics were "an extremely useful tool" for the treatment of infection, but they must be used "appropriately".

One theory as to why antibiotics could lead to cancer suggests that the drugs affect bacteria in the intestine, interfering with the metabolism of certain foods that are known protect the body against cancer and so could be related to the development of cancer.


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