Evaluation of fulvestrant in clinical practice: use of an electronic data registry

Most postmenopausal women with hormone receptor-positive advanced breast cancer eventually develop resistance to endocrine therapy, resulting in disease progression and the need for further treatment. Fulvestrant's distinct mode of action offers the potential to overcome tumor resistance to previous endocrine treatments.

This observational, postmarketing, Web-based surveillance study collected "real-world" information on the use of, and the outcomes associated with, fulvestrant 250-mg-per month treatment of patients with advanced breast cancer in clinical practice.

A total of 213 postmenopausal patients with advanced breast cancer were enrolled from 34 practices throughout the United States. Of these, 200 patients (93.9%) had received previous endocrine therapy. Overall, 85.4% of patients had received previous aromatase inhibitor treatment for early breast cancer, advanced breast cancer, or both. In clinical practice, fulvestrant was most frequently administered as a second-line (46% of patients) or a third-line endocrine treatment (27.7% of patients) for advanced disease. Most patients who discontinued fulvestrant (55.1%) subsequently received cytotoxic chemotherapy. Fulvestrant treatment resulted in clinical benefit for 47.9% of patients; 58 patients (27.2%) exhibited an objective response, of whom 3 exhibited a complete response. The median time to response was 2.1 months, and the median duration of response was 7.6 months. At the time of analysis, 74.6% of patients had experienced disease progression; median time to progression was 4.7 months.

These findings are similar to those reported in the clinical trial setting and confirm that fulvestrant has clinical activity after progression on previous endocrine therapy, including aromatase inhibitors.