Improved breast cancer survival among hormone replacement therapy users is durable after 5 years of additional follow-up

Background: We previously reported that breast cancer patients who used hormone replacement therapy (HRT) had significantly lower stage tumors and higher survival than never-users. We present an update with longer follow-up, HRT use data, and in vitro research. Methods: Our database of 292 postmenopausal breast cancer patients was updated to include HRT type, duration, and disease status. In vitro effects of estrogen (E) and/or medroxyprogesterone (MPA) on breast cancer cell growth were measured. Results: Tumor prognostic factors were better and survival rates higher for both E and combination HRT users of any duration. Use greater than 10 years correlated with node-negative disease, mammographically detected tumors, and 100% survival. E supported minimal proliferation; MPA induced cell death; E+MPA results were similar to E alone. Conclusions: HRT users, regardless of type or duration of HRT use, continued to have higher survival rates. In vitro results supported the clinical finding that outcomes for users of E and E+MPA were similar.