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The effect of acute aromatase inhibition on breast parenchymal enhancement in magnetic resonance imaging: a prospective pilot clinical trial

Mousa, Noha A. MD, PhD1,2,3; Eiada, Riham MD4,5; Crystal, Pavel MD4,5; Nayot, Dan MD1; Casper, Robert F. MD, FRCS(C)1,2,6

doi: 10.1097/gme.0b013e31823772a8
Original Articles

Objective The breast is highly hormonally sensitive especially to the sex steroid hormone estrogen. Both physiological and iatrogenic steroid hormone modifications could affect how the breast tissue may appear in breast imaging techniques. We hypothesized that estrogen deprivation therapy could reduce breast nonspecific enhancement on magnetic resonance imaging (MRI).

Methods This study was a prospective pilot phase II clinical trial. The study was approved by Health Canada and the institutional research ethics board, and participants signed informed consent forms. Sixteen healthy postmenopausal women were enrolled, and 14 completed the study. Baseline breast MRI was done followed 1 month later by administration of a high-dose aromatase inhibitor (letrozole 12.5 mg/day) for 3 successive days before a second breast MRI. Background breast parenchymal enhancement was compared between the pretreatment and posttreatment studies.

Results There was a statistically significant reduction of the average background breast enhancement after treatment with aromatase inhibitors compared with baseline MRI. Of particular interest, specific areas of benign breast enhancement were reduced after aromatase inhibitor treatment. No significant adverse effects were recorded using this relatively high dose of the aromatase inhibitors.

Conclusions This preliminary study provided evidence that aromatase inhibitors could reduce the parenchymal background enhancement of benign breast tissue during MRI and may improve the specificity of the technique.

Supplemental digital content is available in the text.Postmenopausal women were enrolled in this study and their breast background enhancement was analyzed objectively and subjectively before and after treatment.

From the 1Department of Obstetrics and Gynecology, University of Toronto,Toronto, Ontario, Canada; 2Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada; 3Department of Obstetrics and Gynecology, Assiut University, Asyut, Egypt; 4Marvelle Koffler Breast Centre, Mount Sinai Hospital, Toronto, Toronto, Ontario, Canada; 5Department of Radiology, University of Toronto, Toronto, Ontario, Canada; and 6Samuel Lunenfeld Research Institute, Mount Sinai Hospital,Toronto, Toronto, Ontario, Canada.

Received June 23, 2011; revised and accepted August 16, 2011.

Funding/support: The study was funded by the Canadian Foundation for Women’s Health (CFWH). N.A.M. is supported by the health professional and Bisby fellowships from the Canadian Institute of Health Research, and R.F.C. is supported by the Camille Dan Family Research Chair in Translational Cell Biology.

Authors’ Contributions: N.A.M. contributed in study design, patient recruitment and enrollment, data analysis, and writing the manuscript. R.E. carried out the breast magnetic resonance image analysis of the study using image analysis and subjective methods and contributed in the drafting of the manuscript. P.C. assisted in outcome analysis design and in critically reviewing the manuscript. D.N. helped in drafting the manuscript. R.F.C. is the originator of the idea, designed the study, and edited the manuscript. The authors approved the submitted manuscript.

Trial Registration: NCT01129622.

Financial disclosure/conflicts of interest: None reported.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (

Address correspondence to: Robert F. Casper MD, FRCS(C), Division of Reproductive Sciences, University of Toronto, Samuel Lunenfeld Research Institute, Mount Sinai HospitalYToronto, 25 Orde Street, Toronto, Ontario, Canada, M5T 3H7. E-mail:

©2012The North American Menopause Society