Fulvestrant in advanced breast cancer: evidence to date and place in therapy

Abstract

Breast cancer is a classical hormone-dependent tumour; therefore, endocrine therapy is the mainstay of treatment for hormone receptor-positive, human epidermal growth factor 2-negative advanced breast cancer. Until recently, classical endocrine agents such as tamoxifen, steroidal and nonsteroidal aromatase inhibitors and fulvestrant have been widely used in postmenopausal patients to treat locally advanced or metastatic disease. However, for patients with this subtype of breast cancer, the landscape of endocrine therapy is rapidly changing. Therapies targeting oestrogen modulation have evolved in recent years following the introduction of targeted agents, mTOR and CDK 4/6 inhibitors that are administered in combination with hormone therapy. As a result, options for endocrine therapy have expanded in recent years, and a variety of single-agent or combinations of targeted drugs and endocrine therapies are accepted. Fulvestrant is a selective oestrogen receptor downregulator (SERD) which was introduced to clinical practice in 2002, initially with the indication to treat postmenopausal women with hormone-receptor-positive advanced breast cancer as second-line therapy postdisease progression after aromatase inhibitors or tamoxifen. Additionally, fulvestrant has also been shown to be active in patients previously untreated with endocrine therapy, either both in the neoadjuvant and the metastatic setting, alone or in combination with other targeted therapies. Currently, the standard dose is 500 mg, which is administered with a loading dose. Fulvestrant received a new FDA indication in December 2016, in combination with palbociclib, both in pre/peri/postmenopausal women with breast cancer progressing after endocrine therapy. This manuscript aims to give an overview of new efficacy data and the current role of fulvestrant in the systemic therapy of hormone-receptor-positive advanced breast cancer, in the context of other available therapeutic modalities.

Keywords: advanced breast cancer; endocrine therapy; fulvestrant; selective oestrogen receptor downregulator.

Figure 1.

A schematic representation comparing the action of oestradiol (E) with that of tamoxifen (T) and fulvestrant (F). AF1, activation function 1; AF2, activation function 2; E, oestradiol; ER, oestrogen receptor; ERE, oestrogen receptor response element; F, fulvestrant; RNA POL II, ribonucleic acid polymerase II; T, tamoxifen.