To compare the effect of therapy with anastrozole versus a combination of fulvestrant and anastrozole in women in first relapse of endocrine-responsive breast cancer.

Postmenopausal women, or premenopausal women receiving a gonadotropin-releasing hormone agonist, with estrogen receptor- and/or progesterone receptor-positive disease at first relapse after primary treatment of localized disease were open-label randomly assigned to a fulvestrant loading dose (LD) regimen followed by monthly injection plus 1 mg of anastrozole daily or to 1 mg of anastrozole daily alone. The primary end point was time to progression (TTP).

In all, 514 women were randomly assigned to fulvestrant plus anastrozole (experimental arm; n = 258) or anastrozole (standard arm; n = 256). Approximately two thirds had received adjuvant antiestrogens, but only eight individuals had received an aromatase inhibitor. Median TTP was 10.8 and 10.2 months in the experimental versus standard arm, respectively (hazard ratio [HR] = 0.99; 95% CI, 0.81 to 1.20; P = .91); median overall survival was 37.8 and 38.2 months, respectively (HR = 1.0; 95% CI, 0.76 to 1.32; P = 1.00). Incidences of prespecified adverse events (AEs) were similar. Hot flashes were more common in the experimental arm: 63 patients (24.6%) versus 35 patients (13.8%) in the standard arm (P = .0023). Death owing to AEs was reported in 11 (4.3%) and five patients (2.0%) in the experimental versus standard arm, respectively.

Fulvestrant (250 mg + LD regimen) in combination with anastrozole offered no clinical efficacy advantage over anastrozole monotherapy in this population of individuals with a relatively high proportion of previous adjuvant antiestrogen exposure.