By Mary Wessling
ST. GALLEN, Switzerland -- March 16, 2009 -- High-dose fulvestrant is well tolerated and has significantly greater biological activity than normal doses of fulvestrant or than anastrozole in postmenopausal women with advanced hormone receptor-positive (HR+) breast cancer, researchers stated here at the St. Gallen Oncology Conferences: Primary Therapy of Early Breast Cancer International Conference (SGBCC).
Nadia Harbeck, Breast Center Cologne/Frechen, University of Cologne, Cologne, Germany, reported on the analysis of 2 phase 2 trials evaluating high doses (HD) of fulvestrant in postmenopausal women with HR+ advanced breast cancer on March 13.
The Neoadjuvant Endocrine Therapy for Women With Estrogen-Sensitive Tumours (NEWEST) study and the Fulvestrant First-Line Study Comparing Endocrine Treatments (FIRST) study were designed to evaluate whether fulvestrant HD would convey increased antitumour activity versus the currently approved dose (AD) of fulvestrant or anastrozole (1 mg/day) in postmenopausal women with HR+ advanced breast cancer.
The NEWEST trial included 211 patients who were randomised to fulvestrant HD (n = 109) or to fulvestrant AD (n = 102) for 16 weeks prior to surgery.
Analysis of the primary endpoint (clinical benefit rate) demonstrated that fulvestrant HD was at least as effective as anastrozole (72.5% vs 67.0%; odds ratio [OR] 1.30; 95% confidence interval [CI], 0.72-2.38; P = .386). The absolute treatment difference was 5.6% (95% CI, -7.8% to 15.8%).
Treatment-related adverse effects (AEs) were experienced by 37.4% of patients in the fulvestrant HD group and 30.7% of patients in the AD group. Treatment-related serious AEs were experienced by 0.9% in the HD group and 3.0% in the AD group.
The researchers concluded that the NEWEST trial has shown that fulvestrant HD has significantly greater biological activity than fulvestrant AD in the neoadjuvant setting.
In the FIRST trial, 205 patients were randomised to fulvestrant HD (n = 102) or to anastrozole 1 mg (n = 103) as first-line therapy for HR+ advanced breast cancer.
In terms of OR in evaluable patients (fulvestrant HD, n = 89; anastrozole, n = 93), fulvestrant HD was as effective as anastrozole (36.0% vs 35.5%; OR = 1.02; 95% CI, 0.56-1.87; P = .947).
The most common treatment-related AEs in both treatment groups were hot flushes, with 7.9% in the fulvestrant HD group and 12.6% in the anastrozole group. The incidence of serious AEs was 11.9% with fulvestrant HD and 9.7% with anastrozole.
An ongoing phase 3 trial -- Comparison of Fulvestrant in Recurrent or Metastatic Breast Cancer (CONFIRM) -- will provide further clarification of the role of fulvestrant HD in the treatment of postmenopausal women with advanced breast cancer, recurring or progressing on prior endocrine therapy, the researchers concluded.
[Presentation title: High-Dose Fulvestrant (500 mg): Clinical Evidence Supporting Potentially Improved Efficacy Benefits in Hormone Receptor-Positive (HR+) Advanced Breast Cancer (ABC). Abstract 0185]
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