endocrine therapy plays a central
role in the treatment of hormone-receptor
(HR)–positive metastatic breast cancer.1 Selective
aromatase inhibitors, such as anastrozole,
letrozole, and exemestane, lower the estrogen level
and are used as first-line endocrine treatments of
HR-positive metastatic disease, owing to their
superiority over tamoxifen.1 Fulvestrant (Faslodex,
AstraZeneca) is an analogue of estradiol that downregulates
the estrogen receptor by disrupting
estrogen-receptor dimerization and accelerating
degradation of the unstable fulvestrant–estrogenreceptor
complex.2 This effect leads to reduced
cross-talk between the estrogen receptor and
estrogen-independent growth factor signaling,
thus delaying resistance to hormone therapy.2
Clinically, fulvestrant at a dose of 250 mg monthly
is as active as tamoxifen when used as first-line
therapy for metastatic disease3 and as active as
anastrozole when administered in patients who
have had disease progression after receiving tamoxifen
therapy.4,5