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Drug Combination Slows Breast Cancer Relapse
The combination therapy also increased the median time to disease progression for these patients (15.0 months vs. 13.5 months). Progression-free survival was the study’s primary endpoint; overall survival was a secondary endpoint.
Anastrozole and fulvestrant are both used in treating breast cancer, but not in combination. Anastrozole suppresses the production of tumor-promoting estrogen, and fulvestrant blocks the receptors that estrogen uses to drive tumor cells to grow and reproduce. Researchers hypothesized that these two modes of action together could make the combination of these drugs more effective than either drug alone against hormone receptor-positive breast cancer, the subtype seen in more than 50% of all cases of breast cancer.
The paper also reports that 41% of patients in the anastrozole-only arm switched to the fulvestrant arm after their disease progressed on anastrozole, suggesting that combined use of the two agents rather than sequential use underlies the survival benefit seen in the study.
The researchers saw improvement in survival despite the fact that the dosage of fulvestrant used in the trial––250 mg monthly––was only half of the accepted standard.
Read the news release, available here.