Background: Without population-based evidence, some clinicians recommend short-term suspension of hormone therapy to improve the performance of mammography. Hormone therapy increases breast density, and abnormal screening mammograms are more common among women with denser breasts and among women using hormone therapy.
Objective: To test whether 1 to 2 months of hormone therapy suspension before screening mammography decreases additional mammographic imaging (recall) in women age 45 to 80 years.
Design: 3-group randomized, controlled trial.
Setting: Integrated health plan in western Washington from 2004 to 2007.
Patients: 1704 women age 45 to 80 years who used hormone therapy at their most recent screening (index) mammography, were due for screening (study) mammography, and were still using hormone therapy.
Intervention: Block random assignment (by breast density and hormone therapy type) to no hormone therapy suspension (n = 567) or suspension for 1 month (n = 570) or 2 months (n = 567) before study mammography. One blinded expert radiologist interpreted all mammograms.
Measurements: Recall was the primary outcome, and change in mammographic breast density (percentage and dense area) between the index and study mammograms was the secondary outcome.
Results: Mammography recall rates were 11.3% (61 of 542 women in the no-suspension group), 12.3% (50 of 478 women in the 1-month suspension group), and 9.8% (44 of 451 women in the 2-month suspension group). No subgroups were identified in which brief suspension of hormone therapy resulted in decreased mammography recall. With suspension, decreases in percentage of breast density were orderly and statistically significant: 0.1% (no-suspension group), -0.9% (1-month suspension group), and -1.5% (2-month suspension group). Similar ordered decreases were observed for dense area. Women in the suspension groups experienced increased menopause symptoms.
Limitations: Results can only be generalized to women age 45 to 80 years who have used hormone therapy for at least 1 year and will consider short-term suspension; most eligible women (61%) declined participation. Mammography recall was determined by 1 expert radiologist.
Conclusion: Brief hormone therapy suspension was associated with small changes in breast density and did not affect recall rates. No evidence supports short-term hormone therapy suspension before mammography.