5-strain Probiotic Formulation in HR-positive Breast Cancer Receiving Aromatase Inhibitor to Prevent Bone Loss

Inclusion Criteria: * Female age ≥ 18 years * Eastern Cooperative Oncology Group (ECOG) performance status 0, 1, or 2 * Histologically confirmed anatomical stage 0-III hormone receptor-positive breast cancer * Will be starting on an aromatase inhibitor (letrozole, anastrozole, or exemestane) ± ovarian function suppression (OFS) per treating physician's discretion * Absolute neutrophil count (ANC) ≥ 1000/mm\^3 (prior to registration) * Platelet count ≥ 75,000/mm\^3 (prior to registration) * Hemoglobin ≥ 9.0 g/dL (prior to registration) * Creatinine ≤ 2 x upper limit of normal (ULN) (prior to registration) * Serum glutamic-oxaloacetic transaminase (SGOT) (aspartate aminotransferase \[AST\]) ≤ 2 x ULN (prior to registration) * Albumin ≥ 3 g/dL (prior to registration) * Willing and able to provide research stool and blood samples * Negative serum pregnancy test done ≤ 7 days prior to registration, for women of childbearing potential only (\< 60 years old with intact uterus) * Capable of providing valid informed consent * Willing to return to enrolling institution for all study visits (blood draws, etc) Exclusion Criteria: * Requires prolonged systemic antibiotic therapy for other conditions and recent systemic antibiotic ≤ 14 days prior to registration * Fecal microbiota transplant (FMT) ≤ 6 months prior to registration * FMT with an associated serious adverse event related to the FMT product or procedure * Co-morbid systemic illnesses or other severe concurrent diseases which…