Faslodex Comparable to Arimidex in Phase 3 Trials

For postmenopausal women diagnosed with locally-advanced or metastatic breast cancer, results from a phase 3, randomized, multicenter trial that compared the safety and efficacy of Faslodex (fulvestrant; AstraZeneca) vs Arimidex (anastrozole; AstraZeneca) as first-line endocrine in this setting showed a significant improvement in progression-free survival (PFS) with Faslodex.

The FALCON (Fulvestrant and Anastrozole Compared in hormonal therapy Naïve advanced breast cancer) found that the median PFS in women treated with fulvestrant was 16.6 months compared to 13.8 months for women treated with Arimidex (P = 0.04).

More recent results of a pre-specified subgroup analysis found that the improved PFS seen with fulvestrant is largely consistent across subgroups analyzed by the investigators. For women with non-visceral disease (or in whom disease has not spread to the organs within the chest or abdomen), Faslodex was associated with a decreased risk of disease progression in 41% (HR 0.592; 95% CI:0.419-0.837) compared to those treated with Arimidex. Compared to the 22.3 months median PFS in women treated with Faslodex, those treated with Arimidex had a 13.8 month PFS.

 No difference in PFS was seen in patients with visceral disease, however, with a comparable treatment effect seen for both treatments (HR 0.993; 95% CI: 0.740-1.331). 

In terms of safety, the subgroup analysis found that serious adverse events occurred in 11.6% of patients with non-visceral disease treated with Faslodex versus 16.8% in those treated with Arimidex. In patients with visceral disease. 14.3% of patients treated with fulvestrant and 10.1% of patients treated with Arimidex had a serious adverse event.

The subgroup analyses were recently presented at the 2016 San Antonio Breast Cancer Symposium. —Mary Beth Nierengarten