How does antibiotic use affect a women's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Several large database studies including Group Health Cooperative and the Saskatchewan prescription database show an increased risk with long-term use that rises to a twofold increase with over a total of 1,000 days of use. Other comparable pharmacy record systems (such as Denmark) have not shown as strong a relation. No clear drug class effect has been observed. This evidence, though still evolving, nevertheless points to the possibility that modification in the gut microbiome through extended use of antibiotics may significantly modify risk of breast cancer.

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