Estrogen replacement therapy after localized breast cancer: Clinical outcome of 319 women followed prospectively

Purpose: to determine whether estrogen replacement therapy (ERT) alters the development of new or recurrent breast cancer in women previously treated for localized breast cancer. Patients and Methods: Potential participants (n = 319) in a trial of ERT af ter breast cancer were observed prospectively for at least 2 years whether they enrolled onto the randomized trial or not. Of 319 women, 39 were given estrogen and 280 were not given hormones. Tumor size, number of lymph node s, estrogen receptors, menopausal status at diagnosis, and disease-free int erval at the initiation of the observation period were comparable for the t rial participants (n = 62) versus nonparticipants (n = 257) and for women o n ERT (n = 39) versus controls (n = 280). Cancer events were ascertained fo r both groups. Results: Patient and disease characteristics were comparable for the trial participants versus nonparticipants, as well as for the women on ERT versus the controls, One patient in the ERT group developed a new lobular estroge n receptor-positive breast cancer 72 months after the diagnosis of a ductal estrogen receptor negative breast cancer and 27 months after initiation of ERT. In the control group, there were 20 cancer events: 14 patients develo ped new or recurrent breast cancer at a median time of 139.5 months after d iagnosis and six patients developed other cancers at a median time of 122 m onths. Conclusion: ERT does not seem to increase breast cancer events in this subs et of patients previously treated for localized breast cancer. Results of r andomized trials are needed before any changer in current standards of care can be proposed, J Clin Oncol 17:1482-1487. (C) 1999 by American Society o f Clinical Oncology.