Effects of Different Hormone Therapies on Breast Pain in Recently Postmenopausal Women: Findings from the Mayo Clinic KEEPS Breast Pain Ancillary Study

Background: It is estimated that 70% of women in Western societies experience breast pain at least once during their lifetime. In the Women's Health Initiative (WHI), women treated with oral conjugated equine estrogen (0.625 mg) with or without continuous oral medroxyprogesterone acetate (2.5 mg) had a higher incidence of breast pain than those who received placebo. The effect of other hormone therapy regimens on breast pain is unknown. We compared breast pain among healthy, recently menopausal women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS) at Mayo Clinic. Methods: Women were randomized to: 0.45 mg/day oral conjugated equine estrogen (o-CEE) plus 200 mg/day micronized progesterone (m-P) for the first 12 days of the month, 50 mu g/day transdermal 17 beta estradiol (t-E2) plus m-P for 12 days, or placebo pills and patch. Participants completed the Mayo Clinic breast pain questionnaire at baseline and yearly for the duration of the study. Results: Participants (116) averaged 53.0 years of age and 1.6 years past their last menses at baseline. At baseline, 12 women (10%) reported breast pain with an average worst pain score [from 0 (no pain) to 10 (worst pain)] of 0.39 +/- 1.28. With treatment, the number of women reporting pain did not increase, and with either intention-to-treat or per-protocol analyses, breast pain scores did not differ significantly (p=0.39) among groups: t-E2 (0.53 +/- 1.21), o-CEE (0.32 +/- 0.78), placebo (0.23 +/- 0.87). Conclusion: Four years of treatment with o-CEE at a lower dose than that studied in the WHI with cyclic m-P or transdermal E2 with cyclic m-P did not increase breast pain in healthy, recently menopausal women.