Do Aromatase Inhibitors (AIs) Decrease Intestinal Calcium Absorption?

Study Overview
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Brief Summary
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Research Question: Do Aromatase Inhibitors Decrease Intestinal Calcium Absorption? Study Design: Postmenopausal women with early stage breast cancer initiating aromatase inhibitor adjuvant therapy will participate in this two-month study. The primary study outcome is the change in intestinal calcium absorption following such therapy. Secondary outcomes are the changes in bone resorption markers and musculoskeletal signs and symptoms after initiation of therapy. We will interview women and review their medical records to determine eligibility. Eligible subjects will undergo two calcium absorption studies. The first study will determine their baseline calcium absorption, and the second study will occur after taking an aromatase inhibitor daily for at least 6 weeks. Women will present to the research unit in the early morning and receive an oral and intravenous stable calcium tracer with breakfast. Over the next 24 hours, we will collect all urine for measurement of its calcium content. During each inpatient stay, we will assess musculoskeletal symptoms by questionnaire and joint examination. Each woman will complete a four-day diet diary twice during the study.

Official Title
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Do Aromatase Inhibitors (AIs) Decrease Intestinal Calcium Absorption?

Conditions
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Breast Cancer, Osteoporosis, Osteopenia, Fracture

Intervention / Treatment
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* Drug: Aromatase Inhibitor


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Women at least 5 years past menopause, defined as date of last menses or bilateral oophorectomy Newly diagnosed breast cancer and starting an AI as initial adjuvant therapy Exclusion Criteria Recent, current or planned chemotherapy for breast cancer, as this may have independent effects on intestinal health, calcium homeostasis and bone turnover Allergy or intolerance to orange juice, as one isotope is given with orange juice Current use of over-the-counter or prescription antacids, as they may influence Ca-Ab Intestinal conditions associated with malabsorption or low gastric acid levels including Crohn's disease, ulcerative colitis, pernicious anemia, bacterial overgrowth, celiac sprue, chronic diarrhea or use of antibiotics within the past month Known Stage 4 or 5 Chronic Kidney Disease, defined as an estimated GFR <30 cc/minute Use of medications known to interfere with calcium or vitamin D metabolism, including oral steroids or anticonvulsants Significant lymphedema precluding adequate intravenous access
Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: aromatase inhibitor therapy<br>aromatase inhibitor therapy for six weeks | Drug: Aromatase Inhibitor<br>* Any aromatase inhibitor started as initial adjuvant therapy<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Intestinal Calcium Absorption Related to Aromatase Inhibitor Therapy | intestinal calcium absorption | baseline and 6 weeks later |