title: Aromatase inhibitors and calcium absorption in early stage breast cancer.
abstract: To investigate the effect of aromatase inhibitors (AI) on intestinal calcium absorption, measured using the gold-standard dual stable calcium isotope method. In this pilot study, we recruited 10 postmenopausal women with hormone receptor-positive breast cancer who planned to initiate AI therapy; women receiving chemotherapy were excluded. Women completed two 24 h inpatient calcium absorption study visits, the first prior to AI therapy and the second at least 6 weeks following onset of AI therapy. We calculated total fractional calcium absorption (TFCA) using the dose-corrected fractional recovery of two stable isotopes from 24 h urine collections. Ten postmenopausal women (mean±SD age, 66±7 years; 25(OH)D 40±7 ng/mL, and total calcium intake of 1,714±640 mg/day) exhibited no change in TFCA related to AI therapy (0.155±0.042 prior to and 0.160±0.064 following AI therapy, p=1.0). Subjects exhibited a surprisingly small decline in serum estradiol levels with AI therapy that was not statistically significant. However, there was a significant correlation between duration of AI therapy and the decline in serum estradiol levels (r=-0.65, p=0.040). In this pilot study, AI therapy did not decrease TFCA. Women with early stage breast cancer exhibited an unexpectedly low TFCA, most likely due to their high calcium intake. The null effect of AI therapy on TFCA might relate to the brief duration of AI therapy, the minimal effect of AI therapy on estradiol levels, subjects' high calcium intake or excellent vitamin D status.
authors.affiliation: University of Wisconsin School of Medicine and Public Health, Room 4124, 1685 Highland Avenue, Madison, WI, 53705-2281, USA.
authors.forename: Amye
authors.initials: A
authors.lastname: Tevaarwerk
authors.forename: Mark E
authors.initials: ME
authors.lastname: Burkard
authors.forename: Kari B
authors.initials: KB
authors.lastname: Wisinski
authors.forename: Martin M
authors.initials: MM
authors.lastname: Shafer
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Davis
authors.forename: Jyothi
authors.initials: J
authors.lastname: Gogineni
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Crone
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hansen
mesh_terms: D000368:Aged; D000077384:Anastrozole; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology* / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000097:blood / Q000188:drug therapy / Q000378:metabolism*; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D004032:Diet; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D008875:Middle Aged; D009376:Neoplasms, Hormone-Dependent / Q000097:blood / Q000188:drug therapy / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology* / Q000627:therapeutic use; D017698:Postmenopause; D014230:Triazoles / Q000494:pharmacology* / Q000627:therapeutic use; D014807:Vitamin D / Q000097:blood
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D014807:Vitamin D; D000077384:Anastrozole; D002118:Calcium