Background: Breast cancer tumors occurring in hormone replacement therapy (HRT) users are less aggressive, but no studies have compared tumor aggressiveness among HRT users by length and mode of therapy.
Methods: A total of 1105 consecutive postmenopausal patients treated for operable breast cancer at the European Institute of Oncology were identified. Women exposed to HRT were compared with HRT nonusers by clinical stage at presentation and pathologic and biological tumor characteristics. HRT duration and administration modality were analyzed in relation to tumor characteristics in the HRT group.
Results: Better stage distribution, including smaller pathologic tumor diameter and fewer involved axillary lymph nodes, was seen in the HRT group. Estrogen receptor-positive tumors were more frequent in the control group, but this tendency was reversed with longer exposure to HRT. Histological grade III tumors were less frequent in the HRT group. More favorable prognostic factors were associated with HRT >5 years. The proliferative fraction was higher in patients with exposure <1 vs. >5 years and in oral versus transdermal users.
Conclusions: Breast cancers developing during HRT have better prognostic characteristics than those seen in HRT nonusers. A trend toward better prognostic characteristics with increasing duration of HRT was seen.