Intestine Bacteria and Breast Cancer Risk

Background: \- Some bacteria found in the large and small intestines help keep people healthy and aid digestion. They may also affect a person s risk of developing cancer. Researchers want to study the relationship between intestinal bacteria and breast cancer risk factors. They can do this by looking at stool and urine samples from postmenopausal women. Objectives: \- To study intestinal bacteria and its relationship to urine-based markers of breast cancer risk in women. Eligibility: \- Women between 55 and 69 years of age with a recent mammogram that showed no signs of cancer. Design: * Participants will be screened with a medical history and basic health questionnaire. * At home, participants will complete questionnaires about cancer risk factors and food consumption. * Participants will also collect urine and stool samples. They will send the samples to the designated labs for study. * No treatment will be provided as part of this protocol.