Magnetic Resonance Imaging quantification of breast density in BRCA carriers following gonadotropin releasing hormone agonist (GnRHA)-based hormonal chemoprevention

Abstract

1506 Background: Breast tissue density limits the usefulness of mammography as a surveillance tool in young women. Breast Magnetic Resonance Imaging (MRI) provides high tissue contrast and three-dimensional structural information not impaired by high breast density. We developed a volumetric “MR density” measure of breast structural composition that may be complementary to mammographic breast density. We tested this MR density measure in unaffected women with known high risk of breast cancer due to a BRCA gene mutation (or empiric risk > 30% lifetime), who were recruited in a phase II trial to study the effects of a hormonal chemoprevention regimen. Methods: Nine premenopausal high-risk women age 21 to 48 were treated with intranasal GnRHA (deslorelin), low-dose estradiol, and testosterone daily for 10 months. All patients underwent one contrast-enhanced breast MRI exam before and after treatment. We measured MR density as the ratio of fibroglandular tissue volume to total volume of the breast, at both time points. Our technique involved the semi-automated delineation of the breast and the automated segmentation of fibroglandular from adipose tissue. An “MR index” was also defined to quantify partial voluming effects due to the presence of adipose/fibroglandular edges in the MR data. Results: Eight out of nine patients showed a reduction in MR density (p = 0.026) with treatment. Three patients had less than 5% MR density at baseline, making it difficult to quantitate a change with treatment. All of the remaining six patients had reduced MR density after treatment (mean reduction 35.5%; p = 0.035). Conclusions: We have demonstrated the use of breast MR density as a robust volumetric quantitative measure of breast tissue composition. Our findings suggest that MR could be used to measure hormonal chemoprevention effects in BRCA carriers. [Table: see text]