Rita S. Mehta, M.D., from the University of California Irvine Medical Center in Orange, and colleagues randomly assigned postmenopausal women with previously untreated hormone receptor-positive metastatic breast cancer to receive either 1 mg of anastrozole orally every day (group 1), with crossover to fulvestrant alone strongly encouraged if the disease progressed, or to a combination of anastrozole and fulvestrant (group 2) in a 1:1 ratio.

The researchers found that the median progression-free survival was 13.5 months in group 1 and 15.0 months in group 2 (hazard ratio [HR] for progression or death with combination therapy, 0.80; P = 0.007 by the log-rank test). In all subgroups the combination therapy was more effective than anastrozole alone, with no significant interactions. Despite the fact that 41 percent of the patients in group 1 crossed over to fulvestrant after progression, overall survival was longer with combination therapy (median, 41.3 months in group 1 versus 47.7 months in group 2; HR for death, 0.81; P = 0.05 by the log-rank test). In group 2 there were three deaths possibly associated with treatment. There was no significant difference in the rates of grade 3 to 5 toxic effects between the groups.

"The combination of anastrozole and fulvestrant was superior to anastrozole alone or sequential anastrozole and fulvestrant for the treatment of hormone receptor-positive metastatic breast cancer, despite the use of a dose of fulvestrant that was below the current standard," the authors write.

The study was partially funded by AstraZeneca, which manufactures anastrozole and fulvestrant; several authors disclosed financial ties to pharmaceutical companies, including AstraZeneca.

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