Owing to its favourable tolerability profile versus cytotoxic
chemotherapy, endocrine
therapy is the treatment of choice for postmenopausal women with
hormone receptor-positive advanced
breast cancer (ABC). However, tolerability concerns associated with some endocrine treatments and the potential for cross-resistance has helped to drive the need for new, effective and better-tolerated agents.
Fulvestrant is a new type of oestrogen receptor antagonist with no agonist effects. In phase III trials,
fulvestrant has been shown to be at least as effective as the third-generation
aromatase inhibitor (AI)
anastrozole in the treatment of postmenopausal women with ABC progressing on prior
tamoxifen therapy.
Fulvestrant is administered as a once-monthly 250 mg
intramuscular injection into the gluteus muscle. Here we review the tolerability of
fulvestrant in the treatment of postmenopausal women with
hormone-sensitive ABC and compare it with that of the four most frequently prescribed endocrine treatments for advanced disease (
tamoxifen,
anastrozole,
letrozole and
exemestane). Compared with these agents,
fulvestrant is well tolerated and is associated with a lower incidence of joint disorders compared with the non-steroidal AIs and none of the potential androgenic side-effects that are sometimes seen with steroidal AIs. It is also associated with hot flushes compared with
tamoxifen.
Fulvestrant therefore provides clinicians and patients with a useful, well-tolerated option for the treatment of
hormone-sensitive ABC. Integration of such agents into the endocrine treatment sequence may extend the opportunity for using well-tolerated
therapies before
chemotherapy needs to be considered and thus may improve quality of life for patients with ABC. The overall safety profiles of newer agents such as
fulvestrant will become increasingly clear with their ongoing use.