Mammographic breast density and tolerance for short-term postmenopausal hormone therapy suspension.

BACKGROUND: Breast density tends to decrease when women stop taking hormone therapy (HT). Some women find HT cessation difficult to tolerate, possibly because of fluctuations in endogenous hormone levels and vasomotor symptoms. We hypothesized that women with dense breasts might have lower tolerance for short-term HT suspension than do women with fatty breasts.

METHODS: As part of the Radiologic Evaluation And breast Density (READ) trial, we randomly assigned 881 women aged 45-80 with a prior screening (index) mammogram to suspend HT for 1 or 2 months before their next screening (study) mammogram. We measured continuous breast density on index mammograms using computer-assisted thresholding. At study mammograms, women indicated tolerance for stopping HT from 1 (extremely difficult) to 7 (very easy). Using linear regression, we evaluated the association between index breast density and tolerance after cessation, adjusting for age, body mass index (BMI), HT type, randomization group, and vasomotor symptoms.

RESULTS: A higher percentage of breast density was associated with lower unadjusted mean tolerance scores (tolerance 4.27, 95% confidence interval [CI] 3.77-4.77 for women with > or =50% density, and 4.73, 95% CI 4.45-5.01 for women with <10% density, not a statistically significant difference). In adjusted analyses, neither percent breast density nor dense breast area was associated with tolerance for HT suspension.

CONCLUSIONS: Although HT use affects breast density, tolerance for suspending HT is not associated with breast density. Women with dense breasts have the greatest potential for decreases in density after HT cessation; they should tolerate stopping HT as well as women with fatty breasts.