This phase II trial tests how well a probiotic, WBF-038, works in preventing bone loss in patients with early-stage hormone receptor-positive breast cancer who are starting treatment with aromatase inhibitors. Aromatase inhibitors are a drug that blocks the activity of an enzyme called aromatase, which the body uses to make estrogen in the ovaries and other tissues. Blocking aromatase lowers the amount of estrogen made by the body, which may stop the growth of cancer cells that need estrogen to grow. Aromatase inhibitors are used to treat some types of breast cancer or to keep it from coming back. Aromatase inhibitors can affect bone health, weight, blood sugar, and waist size. WBF-038 is a combination of both prebiotics and probiotics, designed to improve metabolic health. Giving WBF-038 may improve bone turnover, bone health, blood sugar, weight, and waist circumference in patients with early-stage hormone receptor-positive breast cancer starting on adjuvant endocrine therapy with an aromatase inhibitor.
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
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, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of over-the-counter probiotics
Single group
Biospecimen Collection
Procedure/SurgeryUndergo blood sample collection
Bone Mineral Density Test
Procedure/SurgeryUndergo BMD
Questionnaire Administration
Other interventionAncillary studies
WBF-038
DrugGiven WBF-038 PO
Change in C-terminal telopeptide of type 1 collagen (CTx)
Assessed by standard lab tests at baseline (at study enrollment/eligibility assessment before any therapy) followed by 6 study visits. Participants receive aromatase Inhibitor (AI) therapy followed by a one-year course of probiotic WBF-038.
Change in lumbar spine mineral density
Will be measured by central dual energy x-ray absorptiometry. Participants receive aromatase Inhibitor (AI) therapy followed by a one-year course of probiotic WBF-038.
Change in hip bone mineral density
Will be measured by central dual energy x-ray absorptiometry. Participants receive aromatase Inhibitor (AI) therapy followed by a one-year course of probiotic WBF-038.
Incidence of adverse events
Will be assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.
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