MAMMOGRAPHIC DENSITY IN WOMEN ON POSTMENOPAUSAL HORMONE REPLACEMENT THERAPY

Background. Studies have suggested that mammographic density and patte rn are affected by hormone replacement therapy (HRT) and may influence breast diagnosis. Because 40% of breast cancers diagnosed at our cent er are mammographically detected while still clinically occult, mammog raphic sensitivity is crucial. For this reason we studied the effect o f HRT on mammographic density. Methods. During a period of 18 months w e studied consecutive women older than 54 years attending for breast s creening. We recorded HRT use and dosing regimes. A breast density sco re (BDS) was developed and applied to all mammograms. Results. Mammogr ams of 148 HRT users were compared with those of 158 nonusers. HRT use rs had a significantly higher mean density score (4.7 versus 3.4; p < 0.001). Only 11% of non-HRT users had high scores compared with 37% am ong HRT users (p < 0.001). The significant difference remained when wo men were stratified by age. Duration of HRT (longer or shorter than 5 years) did not affect density scores. Conclusions. HRT is associated w ith a significant increase in breast density. In turn, density and mam mographic sensitivity are related. The possibility that increased brea st density will hamper mammographic diagnosis of clinically occult can cers is worrisome.