Response to fulvestrant in heavily pretreated postmenopausal women:a single-center experience

Fulvestrant (`Faslodex') is a new estrogen receptor (ER) antagonist that has no agonist effects. It binds, blocks and accelerates degradation of the ER, leading to a complete abrogation of estrogen-sensitive gene transcription. In postmenopausal women with advanced breast cancer progressing on prior endocrine therapy, fulvestrant is at least as effective as the third-generation aromatase inhibitor (AI) anastrozole.In this single-center experience, 42 postmenopausal patients with metastatic breast cancer who had been heavily pretreated with prior endocrine therapy and chemotherapy were treated with fulvestrant. Prior endocrine therapies included selective ER modulators (including tamoxifen and toremifene), AIs, megestrol acetate, and high-dose estrogens. In total, eight patients (19%) achieved stable disease (SD) for ≥24 weeks, including two patients with SD for 2 years and one with SD for 14 months. Fulvestrant was well tolerated with the majority of adverse events related to the site of metastatic disease.These data demonstrate that fulvestrant is a well tolerated and effective endocrine therapy for postmenopausal women with metastatic breast cancer who have been heavily pretreated with prior therapies. The novel mechanism of action of fulvestrant reduces the likelihood of cross-resistance with other endocrine therapies and therefore this agent may be active in patients who have proved to be resistant to treatments such as tamoxifen or AIs. The use of fulvestrant earlier in the sequence of endocrine treatments may achieve better responses than observed in this heavily pretreated patient population.