Postmenopausal estrogen replacement therapy is associated with adverse breast cancer prognostic indices

Previous studies have reported that breast cancer patients who used estroge n replacement therapy (ERT) have more favorable tumor characteristics and d ecreased mortality compared with nonusers. However, these findings may be d ue partly to increased medical surveillance in ERT users and detection of e arly stage tumors. Postmenopausal women with biopsy-proven breast cancer (n = 108) were identified based on their participation in screening mammograp hy. Based on self-administered questionnaires completed at the time of mamm ography, 29 of these were users of ERT. Tumor characteristics (histology si ze, nodal status, and estrogen receptor content) of ERT users were compared with those of nonusers. After adjusting for potentially confounding variab les, the odds ratios (OR) describing the relationship between ERT use and t he risk of invasive histopathology (OR = 1.35, 95% CI = 0.48, 3.75), positi ve nodes (OR = 2.43, 95% CI = 0.59, 10.10), size greater than or equal to 2 .0 cm (OR = 2.34, CI = 0.66, 8.27), or negative estrogen receptor status (O R = 1.08, 95% CI = 0.18, 9.38) were >1, although none reached statistical s ignificance. When the subjects were separated into two prognostic groups ba sed on the presence or absence of adverse prognostic indices, ERT users had a statistically significantly increased risk of being in the poor prognost ic group (tumor size greater than or equal to 2.0 cm or positive nodes or n egative estrogen receptor content) (OR = 4.48, 95% CI = 1.10, 18.30). The r isk was highest in current users (OR = 6.28, 95% CI = 1.16, 34.00), users f or 5 or more years (OR = 7.77, 95% CI = 1.09, 55.60), and users of nonconju gated estrogen (OR = 9.63, 95% CI = 1.18, 78.60). Although our sample size is small and we do not currently have information on longterm outcomes, the findings from this screening population suggest that ERT may have an adver se effect on important breast cancer prognostic indices.