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Study Shows Link Between Antibiotic Use and Increased Risk of Breast Cancer


A study published today (2/16/2004) in the Journal of the American Medical Association (JAMA)* provides evidence that use of antibiotics is associated with an increased risk of breast cancer. The authors – from Group Health Cooperative (GHC) in Seattle; the National Cancer Institute (NCI), a part of the National Institutes of Health in Bethesda, Md.; the University of Washington, Seattle; and the Fred Hutchinson Cancer Center, also in Seattle – concluded that the more antibiotics the women in the study used, the higher their risk of breast cancer.

The results of this study do not mean that antibiotics cause breast cancer. “These results only show that there is an association between the two,” explained co-author Stephen H. Taplin, M.D., of NCI’s Division of Cancer Control and Population Sciences and formerly of the GHC. “More studies must be conducted to determine whether there is indeed a direct cause-and-effect relationship.”

“This trial suggests another piece in the puzzle of factors that may potentially be involved in the development of breast cancer,” said NCI Director Andrew C. von Eschenbach, M.D. “The NCI will continue to support research into underlying mechanisms of cancer risk.”

The authors of this JAMA study found that women who took antibiotics for more than 500 days – or had more than 25 prescriptions – over an average period of 17 years had more than twice the risk of breast cancer as women who had not taken any antibiotics. The risk was smaller for women who took antibiotics for fewer days. However, even women who had between one and 25 prescriptions over an average period of 17 years had an increased risk; they were about 1.5 times more likely to be diagnosed with breast cancer than women who didn’t take any antibiotics. The authors found an increased risk in all classes of antibiotics that they studied.

Full Article: National Cancer Institute