Among postmenopausal women with advanced, estrogen receptor-positive breast cancer that has progressed or recurred after prior hormonal therapy, a 500 mg dose of Faslodex® (fulvestrant) appears to be more effective than the originally approved 250 mg dose. These results were published in the Journal of Clinical Oncology. As a result of these findings, the 500 mg dose was recently approved by the U.S. Food and Drug Administration (FDA).
Each year roughly 200,000 U.S. women are diagnosed with breast cancer. Many of these breast cancers will be hormone receptor-positive, meaning that they are stimulated to grow by the circulating female hormones estrogen and/or progesterone. Treatment of hormone receptor-positive breast cancer often involves hormonal therapies that suppress or block the action of estrogen.
Faslodex—a type of hormonal therapy known as an estrogen receptor antagonist—blocks the actions of estrogen. It’s used for the treatment of metastatic, hormone receptor-positive breast cancer in postmenopausal women who experience cancer progression or recurrence after prior hormone therapy. Until recently, a standard dose of Faslodex was 250 mg.
In order to assess the effects of a higher dose of Faslodex, researchers conducted a Phase III clinical trial known as CONFIRM (Comparison of Faslodex in Recurrent or Metastatic breast cancer). The study compared the 250 mg dose of Faslodex to a 500 mg dose among 736 women in 17 countries.
- Compared with the lower dose, the higher dose of Faslodex delayed cancer progression. Median time to cancer progression was 6.5 months among patients treated with the 500 mg dose and 5.5 months among patients treated with the 250 mg dose.
- After one year 34% of patients treated with the 500 mg dose were alive and free of cancer progression compared with 25% of patients treated with the 250 mg dose.
- No new safety concerns were identified with the 500 mg dose. The most common side effects included nausea, bone pain, back pain, and injection site pain.
The results of this study indicate that the 500 mg dose of Faslodex improves progression-free survival without increasing side effects. Based on these findings, the FDA approved the 500 mg dose for postmenopausal women with hormone receptor-positive, metastatic breast cancer that has progressed after antiestrogen therapy.
Reference: Di Leo A, Jerusalem G, Petruzelka L et al. Results of the CONFIRM Phase III trial compared fulvestrant 250 mg with fulvestrant 500 mg in postmenopausal women with estrogen receptor-positive advanced breast cancer. Journal of Clinical Oncology [early online publication]. September 20, 2010.