Administering anastrozole (Arimidex) and fulvestrant (Faslodex) in combination rather than in sequence extended overall survival by 6 months in women with metastatic breast cancer, researchers reported at the CTRC-AACR San Antonio Breast Cancer Symposium, held December 6-10, 2011, in San Antonio, Texas.

“This most likely will change the standard of care for how we treat these patients,” predicted study coauthor Kathy S. Albain, MD, of the Cardinal Bernardin Cancer Center of Loyola University Medical Center in Maywood, Illinois, in a statement describing her team’s findings.

Anastrozole inhibits the aromatase enzyme-induced estrogen synthesis, and fulvestrant blocks the effects of estrogen in hormone-receptor-positive breast cancer. Albain and colleagues hypothesized that these agents would be effective when used concurrently as first-line therapy of hormone-receptor-positive metastatic breast cancer in postmenopausal women. A total of 707 such patients were randomized to receive the standard regimen of anastrozole therapy followed by fulvestrant when the disease progresses or to combination anastrozole plus fulvestrant.

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The women who received the standard regimen survived a median of 41.3 months, with a median progression-free survival (PFS) of 13.5 months. In comparison, the combination group had a median survival of 47.7 months and a median PFS of 15 months. Among women who had never taken tamoxifen, median PFS was 12.6 months for anastrozole followed by fulvestrant, compared with 17 months for anastrozole plus fulvestrant.

Although the two groups of patients experienced generally similar side effects, the three treatment-related deaths—one due to stroke and two due to pulmonary emboli—occurred among the combination users.